I want to create an android Facebook chat application , i found this open source project .. http://coderrr.wordpress.com/2008/05/06/facebook-chat-api/
but i want to ask
Dig a bit deeper into http://developers.facebook.com/docs/chat/. There are a number of XMPP and related APIs for Java, C#, iOS, and Android alike to be found on the web - or you can base such work on the libpurple API from Pidgin (http://www.pidgin.im/). It would behoove you to become familiar with XMPP concepts.
There is great simple code https://github.com/KanybekMomukeyev/FacebookChat , i used it in my app.
U can integrate fb chat using facebook authentication or by digest md5...the code given there does not use any API keys nor it uses digest md5 authentication... So not sure whether it ll wrk...try it out... the overall architecture would be
app<->xmpp<->BOSH<->Facebook chat Since fb support xmpp protocol u can set an xmpp chat client using lib lik smack,strophe,asmack etc...
refer to http://professionalxmpp.com/..great to start with..gives complete idea on hw to go abt...
Facebook provides their own chat API. See the docs at Integrating with Facebook Chat. They provide sample code in PHP.
You can also use Jabber to authenticate with Facebook. You'll need an application key to ensure this all works.