I remember Gaim and **** used to be cool alternatives but useless because sending music and attachments never seemed to work. What's the best one now? How are the features?
Pidgin works well, though it seems a bit memory heavy for what it offers. I hear Miranda is a good lightweight alternative. I also hear both are a billion times better than Trillian.
The extensions for Pidgin make it a worthwhile application. I especially like the chatlog function and an extension that tells you when someone is typing even before you've begun a convo.