485 open bug reports, 883 open feature requests... they might not all be valid, but there is definitely work to be done. Bug triage is good :-) And documentation (both user-visible and developer-visible (code comments)).

Best thing to do is to find something you don't like and fix it.

Most of us are really picky about the code we'll accept. Use tab indentation. No compiler warnings. Don't do anything to hinder the core/UI split (don't add gtk code to the PRPLs or to files in the core that aren't named gtksomething.c).

Good articles:
http://ometer.com/features.html
http://ometer.com/hacking.html
http://www106.pair.com/rhp/free-software-ui.html

Other stuff by Havoc Pennington.