Coccinella is an open source jabber client with a nice set of features.
Coupled with a whiteboard, Coccinella becomes a useful tool to chat and work on projects with other people on a network. Although it won't let you use multiple accounts, the client is highly flexible, and will allow you to connect to any Jabber/XMPP server, including popular IM clients like MSN Messenger, ICQ and even Google Talk. However you won't be able to make use of the VoIP capabilities and webcam support of these IM services, as Coccinella does not handle them.
The client's interface is simple and uncluttered and you can keep all your messages in an inbox, making them easy to browse by subject, sender or date. Coccinella also offers file transfers, and you can choose your own avatars. Apart from the decent collection of emoticons, you can also import new ones if you have them in jisp format.
The whiteboard is really fun to use and easy to share with as many other users as you want. Coccinella also offers up connections to chatrooms, something we've never really been convinced of, but at least, for people interested, it's there.
Coccinella is a good open source jabber client with a whiteboard and loads of emoticons that can connect to any server. A recommended IM tool.