Unlock All Worlds: iPhone
There is an "easter egg" in the iPhone version of "Angry Birds" that unlocks all of the game's worlds without beating each level. Go to the "World Select" screen and hover over a locked world. Press the back button repeatedly until the "Angry Birds" app closes. Reload "Angry Birds and repeatedly tap the "Play" button when it appears. You'll be in the "Locked Worlds Stage Select" screen. Beat the first level of each world to unlock it.
Unlock All Levels: Chrome Version
Wes Bos, a designer who works with HTML5 and Javascript, came up with a hack that unlocks every "Angry Birds" level in the Google Chrome version. Load Angry Birds and then copy and paste javascript: var i = 0; while (i<=69) { localStorage.setItem('level_star_'+i,'3'); i++; } window.location.reload(); into the Chrome browser. To lock all the levels, copy and paste javascript: var i = 1; while (i<=69) { localStorage.setItem('level_star_'+i,'-1'); i++; } window.location.reload(); into the Chrome browser.
Get Three Stars
You'll need a high score to get three stars in any "Angry Birds" level. Your score is based on number of birds you used and the damage that was caused. Each unused bird is an automatic 10,000 points. When you're going through the level, determine whether an extra bird can create more than 10,000 points worth of damage. If so, use it. To create more damage, experiment with the force and angle you use to throw the bird. Also, attack the lower horizontal support beams at the corners to knock over tall structures. It's usually best to wait for the screen to finish moving before you launch the next bird.
Unlock the Sound Board and Golden Egg Levels
Unlock the Sound Board by completing the first three levels with three stars. To unlock the first golden egg level, complete levels four and five with three stars. To unlock the second golden egg level, press the sun in the "Level Select" screen. To unlock the third golden egg level, watch the credits until the end and then press the golden egg.