As well as providing an online web based chat mechanism in Assembla, you can also use any jabber/XMPP client to talk with the project chat room. This is very useful when you are coding and awaiting some input from another project member. Instead of having to check the web page for updates, register your pidgin client and get the nice new message notifications you are used to, whilst not having to install yet another IM Client. Simply add your details as per the attached picture (changing username to your registered user name).

I left the advanced settings as default, and had no problems connecting.