Load.php - This is probably one of the most important files in SMF. It is responsible for loading just about all data that is used by SMF - member info, permissions, boards, etc. It also handles all session-related operations, censored text and (in 1.1) caching.

cache_get_data', 'Pulls the specified variable from the cache.
cache_put_data', 'If caching is enabled, this function puts data in the cache by calling the appropriate function based on what you\'re using.
cache_quick_get', 'Attempts to retrieve a cache entry, and calls a specified function upon failure.
censorText', 'This function handles all the censored words.
detectBrowser', 'Handles browser detection and sets up the $context[\'browser\'] array.
getBoardParents', 'This function loads and returns information about the specified board and any parents of that board.
getLanguages', 'Loads all available languages.
get_memcached_server', 'Used by cache_get_data() and cache_put_data() to pick a (random) memCache server.
loadBoard', 'This function loads all the information for the board specified in the $board global variable.
loadDatabase', 'Loads up the appropriate "Subs-Db" file and connects to the database.
loadLanguage', 'This function loads the language file associated with the specified template.
loadMemberContext', 'This sets up the $context[\'user\'] array for the specified member.
loadMemberData', 'Loads data for the specified user IDs. Returns an array of all member IDs that data was loaded for, or false if nothing was loaded.
loadPermissions', 'This function loads all the permissions for the current user (uses $user_info global variable).
loadSession', 'This function starts a session (unless one already exists) and loads the session id into the $sc global variable ("sc" = "Session Code" ;)).
loadSubTemplate', 'This loads the specified sub-template, which is a function in an already loaded template.
loadTemplate', 'Loads a template file with the name template_name from the current, default, or base theme.
loadTheme', 'This function loads the theme with the specified ID.
loadUserSettings', 'This function loads user information.
reloadSettings', 'This function (re)loads the $modSettings array.
sessionClose', 'Dummy function used as callback for session_set_save_handler when database-driven sessions are enabled.
sessionDestroy', 'Removes all data for the specified session ID from the database.
sessionGC', 'Session "Garbage Collection" function - deletes old sessions based on the \'databaseSession_lifetime\' setting and the passed value (max lifetime is in minutes). Only used for database-driven sessions.
sessionOpen', 'Dummy function used as callback for session_set_save_handler when database-driven sessions are enabled.
sessionRead', 'Reads and returns the data for the specified session.
sessionWrite', 'Writes the specified session data to the database (first tries updating, and then inserts it as a new row if that didn\'t work).
template_include', 'This function is used by the loadTemplate function to include the template file (include as in the PHP function).

LockTopic.php - This file handles locking and stickying of topics.

LockTopic', 'Locks a topic, toggles between locked/unlocked/admin locked.
Sticky', 'Stickies a topic - toggles between sticky and normal.

LogInOut.php - This file is concerned pretty much entirely, as you see from its name, with logging in and out members, and the validation of that.

checkActivation', 'Checks the activation status of the current user account.
DoLogin', 'Actually logs the user in to the forum.
Login', 'Shows a page for the user to type in their username and password.
Login2', 'Actually logs you in and checks that login was successful.
Logout', 'Logs the current user out of their account.
md5_hmac', 'Password-encryption function used in YaBB SE and SMF 1.0.x. Included in later versions for compatibility.
phpBB3_password_check', 'Encrypts passwords using phpBB3\'s custom encryption method.
validatePasswordFlood', 'Protects against brute force attacks on a member\'s password.

ManageAttachments.php - This file handles a lot of admin functions for managing attachments and uploaded avatars.

ApproveAttach', 'Handles post moderation for attachments.
ApproveAttachments', 'Approves the specified attachments.
attachDirStatus', 'Checks the status of an attachment directory and returns an array of the status key, if that status key signifies an error, and the folder size.
BrowseFiles', 'Show a list of attachment or avatar files.
list_getAttachDirs', 'Prepares the attachment directories for being displayed in the list.
list_getFiles', 'Gets a list of files for browsing.
list_getNumFiles', 'Gets the number of files of the specified type.
MaintainFiles', 'Show several file maintenance options.
ManageAttachmentPaths', 'Handles management of attachment directories.
ManageAttachments', 'Main attachment (and, in 1.1, avatar) management function.
ManageAttachmentSettings', 'Show/change attachment settings.
ManageAvatarSettings', 'Show/change avatar settings.
MoveAvatars', 'Move avatars from or to the attachment directory.
PauseAttachmentMaintenance', 'Temporarily pauses the RepairAttachments function to avoid overloading the server.
RemoveAllAttachments', 'Removes all attachments in a single click.
RemoveAttachment', 'Removes a selection of attachments or avatars.
RemoveAttachmentByAge', 'Remove attachments older than a given age.
RemoveAttachmentBySize', 'Remove attachments larger than a given size.
removeAttachments', 'Removes attachments or avatars based on a given query condition.
Performs general maintenance on attachments:\nRemoves attachments from the database if the file doesn\'t exist anymore\nRecalculates filesize\nRegenerates thumbnails if the thumbnail file for an attachment is missing.

ManageBans.php - This file contains all the functions needed for the ban center.

Ban', 'The main entrance point for all ban center functions.
BanBrowseTriggers', 'Screen for showing the banned enities.
BanEdit', 'The screen for adding new bans and modifying existing ones.
BanEditTrigger', 'The screen for adding new ban triggers or modifying existing ones.
BanList', 'Shows a list of bans currently set.
BanLog', 'Show a list of logged access attempts by banned users.
checkExistingTriggerIP', 'Checks to see if an existing trigger matches the given IP.
ip2range', 'Convert a single IP to a ranged IP.
list_getBanLogEntries', 'Gets the data for displaying ban log entries.
list_getBans', 'Gets a list of ban groups.
list_getBanTriggers', 'Gets a list of all the ban triggers for a particular ban group.
list_getNumBanLogEntries', 'Fetches and returns the total number of entries in the ban log.
list_getNumBans', 'Returns the total number of ban groups.
list_getNumBanTriggers', 'Returns the number of ban triggers of the specified type.
range2ip', 'Converts a given array of ip numbers to a single string.
updateBanMembers', 'Updates the members table to match the new bans.

ManageBoards.php - This file controls all the admin functions for managing and editing boards.

EditBoard', 'Screen for editing and repositioning a board.
EditBoard2', 'Function for handling a submitted form saving the board.
EditBoardSettings', 'Handles a few board and category settings.
EditCategory', 'Screen for editing and repositioning a category.
EditCategory2', 'Function for handling a submitted form saving the category.
ManageBoards', 'Main entry point for all the manageboards admin screens.
ManageBoardsMain', 'Main screen showing all boards and categories.

ManageCalendar.php - Contains functions for managing holidays, events and various calendar-related options and settings.

EditHoliday', 'This function is used for adding/editing a specific holiday.
ManageCalendar', 'The main controlling function for the calendar management stuff.
ModifyCalendarSettings', 'This function handles all calendar-related settings.
ModifyHolidays', 'This function handles adding and deleting holidays.

ManageErrors.php - This file handles the error log and the deletion of said errors.

deleteErrors', 'Deletes all or some of the errors in the error log.
ViewErrorLog', 'Sets all the context up to show the error log for maintenance.
ViewFile', 'Will do php highlighting on the file specified in $_REQUEST[\'file\'].

ManageMail.php - This file is all about mail, how we love it so. In particular it handles the admin side of mail configuration, as well as reviewing the mail queue - if enabled.

BrowseMailQueue', 'Displays the mail queueю
ClearMailQueue', 'This function clears the mail queue of all emails, and at the end redirects to browse.
list_getMailQueue', 'Retrieves all the data for the mail queue.
list_getMailQueueSize', 'Gets and returns the total number of items in the mail queue.
ManageMail', 'This function passes control through to the relevant section. It serves as the main entry point for the Mail Queue stuff.
ModifyMailSettings', 'Handles the management of mail settings.
PauseMaileQueueClear', 'Used for pausing the mail queue.
time_since', 'Little function to calculate how long ago a time was.

ManageMaintenance.php - This file contains functions for various forum maintenance tasks.

AdminBoardRecount', 'This function recounts many forum totals that can be recounted automatically without harm.
ConvertEntities', 'Converts HTML-entities to UTF-8 characters.
convertUtf8', 'Convert both data and database tables to UTF-8 character set.
MaintainCleanCache', 'Cleans the cache.
MaintainDatabase', 'Handles the functionality for the maintain database area.
MaintainDownloadBackup', 'Handling function for database backups.
MaintainEmptyUnimportantLogs', 'Empties unimportant logs.
MaintainFindFixErrors', 'Find and fix all the errors.
MaintainMassMoveTopics', 'Moves topics from one board to another.
MaintainMembers', 'Supporting function for the maintain members area.
MaintainPurgeInactiveMembers', 'Handles purging inactive members.
MaintainReattributePosts', 'Handles re-attributing guest posts to a specified user.
MaintainRemoveOldPosts', 'Removes old posts.
MaintainRoutine', 'Supporting function for the routine maintenance area.
MaintainTopics', 'Supporting function for the topics maintenance area.
Maintenance', 'Shows a list of maintenance options.
ManageMaintenance', 'Main entry point for the forum maintenance screen.
optimizeTables', 'Optimizes all tables in the database and lists how much was saved.
VersionDetail', 'This function parses the comment headers in all files for their version information and outputs that for some javascript to check with simplemacines.org.