Angry Birds just got an update which features a new zone called "Ham 'em High" which includes 30 new levels in a desert/western theme. Also included in this update will be the secret level you'll be able to find (hopefully) while watching the Super Bowl tomorrow and possibly win a trip to the premiere of Rio.
Along with the new zone at its 30 levels is a third section with another 15 but unfortunately that isn't available just yet so you'll see a big "Coming Soon" graphic over the levels. Of course with any new update to Angry Birds comes the possibility of new Golden Eggs to be found! If you find one, let us know and we will add it to our Angry Birds Golden Egg guide!
I'm not sure if it is just me but the backgrounds in the new levels seem a bit more 3D-ish as in the background having more depth with the layered look it seems to have.