there exist a number of platform independent jabber clients. these are either written in java or web-based. for jabber.cc, we chose to use jeti, a java-based client.

various other jabber clients exist. psi, kopete, pidgin and sim are popular jabber clients for the linux platform.

on windows: miranda integrates various protocols, including jabber and icq. so does trillian pro (commercial). psi also runs on windows.

mac users might want to have a look at adium x. the new iChat from Mac OS 10.4 Tiger also supports jabber/xmpp.

wikipedia's article on jabber also contains a list of clients.

please see the security page here on jabber.cc for information on how to establish encrypted connections to jabber.cc. there you can also find the root certificate in a special format as required by psi.