Here's how to do it:
1. Go to a World Select Screen
2. Center a locked world on your screen
3. Hit the back button on your Android phone until you exit Angry Birds
4. Load Angry Birds back up
5. When you see the 'Play' button, tap the button repeatedly
6. You're now inside a locked world
You still need to beat each level to advance in the world but with this method you can start new worlds without finishing the old ones. Howeva be warned! You might not feel the same accomplishment the rest of us honest, hard working folks feel.