I've just posted my annual roundup of significant images from planetary exploration in 2010. I make no claims for these being the "best of 2010" -- the images are selected more to mark significant events in 2010, though I confess some are just chosen because they're spectacular. And anyway, this is space exploration; I think all the images are spectacular.
If you are a Planetary Society member, this article expands upon the "Year in Pictures" feature that you saw in the November/December issue of The Planetary Report. That article went to press in early September so there are lots of additional pictures at the bottom, including this incredible one from Saturn only days ago: