Chax is a collection of minor modifications and additions that make using Apple's iChat more enjoyable.
User list:
Toggle text status visibility of users
Automatically resize the contact list to fit the number of visible users
Set font of names, status messages, and group separators
Show animated user icons
Ability to hide iTunes music store links in text statuses
Idle time included in tooltips
Display Address Book nicknames instead of full names
Option to show a warning before messaging mobile users
Hide the audio/video status icon at the top of the user list
Message a specific screen name for people with multiple screen names
Message window:
Tabbed chats, allowing you to keep all of your chats together in one window
Option to auto-accept text chats, skipping new message notification window
Show status changes directly in the message window
Disable the smiley button in text input lines
Option to open images sent through direct connect directly in Preview
Send away auto-reply only once per conversation
Save and restore window positions for individual screen names
Other:
Unread message notification in the dock Growl notifications for new messages and users changing status
Properly use ICQ accounts without sending text formatting in messages
Automatically set status to away when screensaver is activated
Option to auto-accept file transfers
Hide all iChat windows when iChat is inactive
Always on top option for user lists, text chats, and audio or video chats
Set a custom away auto-reply that is different from the away message
Change the delay of or disable auto-away
New message windows cascade properly instead of always appearing on top of each other
Built-in log viewer
Activity window shows history of user status changes
Warn before quitting while there are active chats
Option to disable pausing of AV chats while there are active file transfers
Disable picture-in-picture in video chats
Automatically reconnect when disconnected
Disable alert sounds when away, idle, or available