Here's a cheat that will help you unlock all worlds on the Android version of Angry Birds. It takes the fun out of playing through each world the game, but at least it lets you see different areas, some of which you may not have otherwise been able to reach.
Know that you will still have to play through individual stages of the game (i.e. World 5-1, World 5-2, etc.), but each world can be unlocked.
1) First, you will go to a world select screen.
2) Then, center a locked world on your screen.
3) Hit the back button on your phone until you exit Angry Birds.
4) Relaunch the game
5) When you see the "Play" button tap it over and over again like crazy.
6) You should be taken to the locked world's stage select screen.
7) If you wish for the world to stay unlocked, you must beat the first level of that world.
In case you haven't picked up the game yet, Android users can get it for free. Follow this link for more information: Angry Birds Free for Android.