I'm looking for an open source project written in Java with a relatively low barrier to entry, ie. not hugely complex, friendly, etc.
My background is mostly in web apps so, that'd be the best place for me to start. Mostly, I'm just looking for some place I can do some stuff in free time and keep my chops polished.
I plan on browsing through various public listings but thought I'd see if the Stack Overflow community had any suggestions. Maybe someone even has a pet project...
This mostly depends on your interesets and knowledge. After knowing this, you can browser perhaps Sourceforge, they should offer some additional search parameters like active contributors count, lines of code etc. This should show you some opportunities.
Many of the Apache Foundation projects are Java. Take a look at them and see what you are interested in.
May be this would help: http://amitksaha.blogspot.com/2008/04/participating-in-open-source-java.html
I tried to make it more comprehensive, but never really made it.
The Apache POI HWPF Apache POI HWPF is even openly advertising the need for someone to take over this project. It is a Java API to handle Microsoft Word files.