The best thing to do is download the source, and take a look. Use AbiWord.
See what you like, see what you don't. Spend a few minutes at bugzilla.
By the time you have done all these things, you'll have a pretty good idea
of what needs worked on, and which of them is of a size you are comfortable
with.
Pick something small to get started. Everyone on the list will be glad to
offer help with any specific issue. Good luck!
Robert Sievers
Open Source Evangelist