Been following the new season now, hmm...
Usagi Drop - I like this one the best, though I procrastinate the most to see it, because it's slow and heartwarming. Sweet animation and Rin is really, really cute. It's a good series all-in-all, different from the rest, at least.
No. 6 - Utopian/dystopian to the max. The story (so far) really isn't anything new - naive kid who grew up in a seemingly-perfect utopia meets savage kid from outside world, learns that people live outside the utopia in misery and third-worldiness, yada yada. Surprisingly, the homosexual relationship hinted between the two main characters is the most interesting part of the anime, followed by the otherwise excellent animation (even though the outside world looks like it's Fallout: The Anime more often than not).
Mawaru Penguindrum - This is the season's WTF anime. The first episode was hilarious all through, but the other episodes not so much. It's absurdist comedy in the vein of Arakawa, but that's also the annoying part about it, because it can't seem to decide if it's wants to deal with something serious or something ridiculous. Terrific music though.
Kami-sama no Memo Chou - It looks like Gosick crossed with Durarara!! with a bit of Angel Beats! and has the strong points of neither. Very slick and well-researched, and will apparently be dealing with social problems in Japan, but it's hard to take the series seriously at times, with its misplaced fan service and steretypical characters. The hero is too cynical to care for, the heroine is too cold and distant, and the side-characters too plain boring. Could have potential later though.