There's an easy way to remove ads when you're playing angry birds: just long-press power and select 'flight mode' before you start the game. It also works for 'Angry Birds Seasons' except that the first time you visit a new xmas level you have to not be in flight mode (I think it checks back with a central server to ensure you've reached the correct date).

Plus as a bonus you can be sure you won't get any annoying phone calls while you're playing. :^)