Bombus is a free software instant messaging client based on XMPP. Its website is in Russian but there is an English help page.
SVN: http://svn.xmpp.ru/repos/bombus/trunk
There is also Bombus NG (New Generation) for Windows Mobile (written in C++). It is also open sourced under GNU GPL.
SVN: http://svn.xmpp.ru/repos/bombus-ng/trunk
Valhalla Chat is aBluetooth Instant Messenger (IM), that provides a common messaging platform for mobile phones, desktop computers and PDA’s.
mobile-google-talk-http is an extension of the MGTalk J2ME application to support the HTTP Binding (JEP-124). The original MGTalk application is a well-done Jabber client for J2ME. It also supports some Google Talk specific features. However, it does not support an HTTP communication mechanism for Jabber (a.k.a HTTP Binding or JEP-124).
MiniIM is a multi-protocol instant messaging client. It is inspired by one of such popular software Pidgin(Gaim). The design is concentrated on the protocol level abstraction and an easy way to integrate new protocol implementations. You can use this client to chat with yahoo/msn/icq/aol contacts.
MGTalk is Jabber client for j2me midp 2.0 platform (midlet), supports some Google Talk features. May run on any j2me midp 2.0 mobile phone or communicator.
kvmjab is a Library for communicating with the Jabber Instant messaging system from either Java 2 Standard Edition or Micro Edition.
k-IRC is totally free java-based mobile application (client) for connecting to any IRC server. It will execute on any handheld device or mobile, supporting Java 2 Micro Edition (actually CLDC1.0/MIDP1.0).
k-IRC allows you to login to an IRC server, enter multiple channels at the same session, talk in the channels and with individuals and receive others’ messages and easily keep the track of active channels and switch between them.
jmIrc is a J2ME MIDlet allowing ie. cell phone owners to use IRC wirelessly. It should work on any device supporting MIDP 1.0 and also supports connecting through HTTP proxy server on phones that don’t support the Java socket API.