I don't really use any FREE apps on a regular basis, even Evernote I pay for the full Pro version as I need the collaboration folders. I guess Dropbox, but I did pay someone $5 to get me 18GB of storage there, so I guess that is not free either, but in a way it still is..
Arf, free app... I'll go for Blogshelf II and Dunno. The later is very useful for research on a subject, and sync with th mac too. The former is a great atom feeds reader that works w/o google account.