Here's a more extensive list of Jabber/XMPP clients:

Desktop :
^ Client                                      ^  Windows    ^  Linux      ^  Mac OS  ^
^ [[http://adium.im/|Adium]]                  |  No         |  No         |  Yes     |
^ [[http://gajim.org/|Gajim]]                 |  Yes        |  Yes        |  Yes     |
^ [[http://talk.google.com/|Google Talk]]     |  Yes        |  No         |  No      |
^ [[http://kopete.kde.org/|Kopete]]           |  No         |  Yes        |  No      |
^ [[http://www.miranda-im.org/|Miranda IM]]   |  Yes        |  No         |  No      |
^ [[http://pandion.im/|Pandion]]              |  Yes        |  No         |  No      |
^ [[http://pidgin.im/|Pidgin]]                |  Yes        |  Yes        |  No      |
^ [[http://psi-plus.com/|Psi+]]               |  Yes        |  Yes        |  Yes     |
^ [[http://swift.im/|Swift]]                  |  Yes        |  Yes        |  Yes     |
^ [[http://www.trillian.im/|Trillian]]        |  Yes        |  No         |  Yes     |

Mobile :
^ Client                                      ^  Java  ^  Android  ^  iOS (iPhone) ^  Symbian  ^  Blackberry  ^  
^ [[http://bombus-im.org/|Bombus]]            |  Yes   |  No       |  No           |  No       |  No          |
^ [[http://www.bombusmod.net.ru/|BombusMod]]  |  Yes   |  No       |  No           |  No       |  No          |
^ [[http://www.shapeservices.com/|IM+]]       |  Yes   |  Yes      |  Yes          |  Yes      |  Yes         |   
^ [[http://www.palringo.com/|Palringo]]       |  Yes   |  Yes      |  Yes          |  Yes      |  No          | 
^ [[http://www.talkonaut.com/|Talkonaut]]     |  Yes   |  Yes      |  Yes          |  Yes      |  No          |
^ [[http://www.trillian.im/|Trillian]]        |  Yes   |  Yes      |  Yes          |  No       |  Yes         |  

You even can connect using a PSP with [[http://pspupdates.qj.net/PSPJabber-v1-03-Released/pg/49/aid/11620|PSPJabber]], or using a Nintendo DS with [[http://theli.is-a-geek.org/blog/static/jabberds|JabberDS]].

Web-based clients: [[http://jappix.org/|Jappix]], [[http://jwchat.org/|JWChat]] and [[http://www.meebo.com/|Meebo]].

For even more clients and also some descriptions, you may visit http://xmpp.org/xmpp-software/clients/.