Not all jailbreak apps are compatible with iOS 4.2.1 so, to make it easier for us to figure out what works and what doesn’t, MuscleNerd has created a list of applications that are compatible with iOS 4.2.1

The list that can be found here is available to anyone to edit. If you want to know what works, and more importantly if you want to help the community, you may want to check out this list and add your own entries.