The launch seems to be getting a lot of attention -- so much so that Rovio had to take its site down. Likewise, the download location is also currently slammed, and GetJar suggests you try to download the game from its mobile site, directly from your Android device.
In case you've never experienced Angry Birds, it's sort of like Boom Blox turned sideways. You use a slingshot to launch birds at a series of structures, with the goal of bringing those structures down around the evil, egg-stealing pigs that inhabit them.
Update: Reader Marcus reports that the game is avaiable on the Android Market. Well, that makes things a bit easier.