Here's a more extensive list of Jabber/XMPP clients:
Desktop :
| Client | Windows | Linux | Mac OS |
|---|---|---|---|
| Adium | No | No | Yes |
| Gajim | Yes | Yes | Yes |
| Google Talk | Yes | No | No |
| Kopete | No | Yes | No |
| Miranda IM | Yes | No | No |
| Pandion | Yes | No | No |
| Pidgin | Yes | Yes | No |
| Psi+ | Yes | Yes | Yes |
| Swift | Yes | Yes | Yes |
| Trillian | Yes | No | Yes |
Mobile :
| Client | Java | Android | iOS (iPhone) | Symbian | Blackberry |
|---|---|---|---|---|---|
| Bombus | Yes | No | No | No | No |
| BombusMod | Yes | No | No | No | No |
| IM+ | Yes | Yes | Yes | Yes | Yes |
| Palringo | Yes | Yes | Yes | Yes | No |
| Talkonaut | Yes | Yes | Yes | Yes | No |
| Trillian | Yes | Yes | Yes | No | Yes |
You even can connect using a PSP with PSPJabber, or using a Nintendo DS with JabberDS.
Web-based clients: Jappix, JWChat and Meebo.
For even more clients and also some descriptions, you may visit http://xmpp.org/xmpp-software/clients/.