The free instant-messaging client Gaim (GDK+ AOL Instant Messenger) has become popular in recent years because of its ability to connect with a wide range of IM networks (Yahoo, MSN, IRC, Jabber/Google Talk/XMPP, AIM, ICQ, Gadu-Gadu, and others) and its extensibility in the form of user-created plug-ins.
The name Gaim came about due to complaints from AOL about the name GDK+ AOL Instant Messenger. However, as AOL Instant Messenger became more popular, AOL trademarked the acronym "AIM," leading to further legal struggles with the Gaim developers. After a series of negotations, the developers agreed to change the name of the 2.0 version of Gaim to Pidgin, based on the word for simplified speech between people who do not share a common language.
The big change in Pidgin 2.0 is the new look. The interface has been redesigned, with the option to view your Buddy List in Basic or Advanced view. Important facets like plug-ins and status availability have been broken out of the Preferences dialog and into areas of their own. Plug-ins have their own dialog available from the Tools menu, and status is now set by a drop-down menu at the bottom of your buddy list.
There's still a long way to go for Pidgin to compete with highly polished clients like Windows Live Messenger, Yahoo Messenger, and Trillian. Pidgin does not include any voice chat options, nor the ability to hook up your webcam.
The strength of Pidgin/Gaim, however, is in its extensibility, and the new Pidgin 2.0 comes packaged with 22 plug-ins included that you can easily enable or disable. The plug-ins have been moved out of Preferences in version 2.0 and into their own dialog, with a helpful "+" sign that gives you more information about any individual add-on.
One of the coolest is Christopher O'Brien's Psychic Mode, which tells you when someone is writing you a message...before they even send it. Another plug-in of note is Sadrul H. Chowdhury's Autoaccept, which lets you automatically accept files sent from specific buddies. While it's easy to enable and disable the included plug-ins and learn more about them, there's no easy way to remove them from your system in the main interface, nor any way to learn about or add new plug-ins.
One other quibble: if you select "Online help" from the Pidgin Help menu, you'll be greeted with an unfortunate 404 error: "The requested URL /documentation.php was not found on this server." Since Pidgin 2.0 only launched today, we'll cut the developers some slack. But if that help documentation isn't live tomorrow ... ;)
For more information about other multiplatform IM software, be sure to check out Jessica Dolcourt's post One IM to rule them all? from yesterday.