By far the best app out there that I have found is GCz, it's free and works really well. I have used the current app and it downloads and posts to Geocaching.com, easy to search right around where you are and integrates a lot of features the pay for apps don't have. A new version is currently in development with the help of the community. A current thread over at XDA is here
http://forum.xda-developers.com/showthread.php?t=482249.