Angry Birds v1.5.3 was recently released. I recommend that you download it.
Also 'Angry Birds Seasons' is available which includes:
Season's Greetings (which is for the Christmas Season)
Trick or Treat (which is for the Halloween season)
Hogs and Kisses (which was released for Valentine’s Day) and
Go Green, Get Lucky (which was released a few days ago for Saint Patrick's Day)