People already mentioned a lot of others that I might have included, so I'll skip over those for the most part. Among the newer series this year, I'm getting to like True Tears a lot, as well as Spice and Wolf. The second season of Sayonara Zetsubou Sensei (preceded by the heading "Zoku" for the second season) is approaching the level of the first season -- see (
http://www.youtube.com/watch?v=NheYjFElRno ) -- and part of it is just how much more random it is. Though, it's a little harder to find, and AFAIK, no one has been subbing it since episode 4.
To cover certain caveats about aforementioned shows in the thread... Gundam 00 and the second season of Shakugan no Shana are both very good, though I have to add that both shows took a few episodes to get there. Similarly, Naruto Shippuuden is sometimes good, sometimes very disappointing. It smacks that the producers are terrified of drawing too close to the manga's story position so they pace it very slowly to avoid the danger. While this is still better than having 2 years of pointless fillers about finding insects and such, it's somewhat paining to have all the good episodes separated by several episodes of endless chatter (and the worst part is that if you read the manga, you'd know that it's not entirely *pointless* chatter)
Hayate no Gotoku is hilarious, though with all the outside anime references, some of the punchlines may be easy to miss. Other truly hilarious shows with loads of game and anime references include Lucky Star and Clannad. Clannad being overall carrying themes like those of Air or Kanon, but with a great deal more comedy interjected into it -- see
http://youtube.com/watch?v=9d_UknfiKMI or
http://youtube.com/watch?v=WcD4o8w0U1U
Among the older series of crazed hilarity include Jungle Ha Itsumo Hale nochi Guu. Another of my favorites from the olden days is Kodomo no Omocha (aka Kodocha), which covers the entire gamut from outright craziness to tear-jerker in one sweep. Hilarious in a more "Seinfeld"-ish way would be Azumanga Daioh.
Something of a surprise for me this season was Shion no Ou -- I figured it would be something like Hikaru no Go, except for Shougi instead of Go (and I did enjoy Hikaru no Go, after all). Turns out that the Shougi is sort of backdrop for a sort of murder mystery storyline. I'm generally not a fan of mystery series because so many of them follow in the vein of Detective Conan (aka "Case Closed" in the US). But one rather old (though subbing was long in coming so subbers only recently finished the series) mystery series that I liked was Karakuri Zoushi Ayatsuri Sakon (usually just shortened to Ayatsuri Sakon), which exudes an overall darker atmosphere that I happen to like.
I'm surprised, though, that for all the series mentioned thus far in the thread that no one has mentioned Tengen Toppa Gurren Lagann.