The default sync app works fine with WINE without any tweaking, for what it's worth. Been using it on Fedora for a few months.

OpenHatch lists tasks from various open-source projects, usually aimed at new contributors - http://openhatch.org/search/ - any project listed there would be actively looking for help and welcoming to new people.

From my experience though, just about every open-source project out there would love to have more people helping out. Have a look at the project's bug tracker.