Apple is famous for tightly controlling the App Store and what programs become available to users of iPhone OS devices (iPhone, iPod touch, and iPad). Some users aren’t satisfied with Apple’s judgment, though, and have created ways to install any application they want on their device and even to use them on carriers other than AT&T. This is called jailbreaking.
Jailbreaking has long been available for the iPhone and iPod touch, but can you jailbreak iPad?
The short answer is yes. There are a handful are of jailbreak tools available for the iPad. Using them will allow you to install non-App Store apps onto the device and, if you have an iPad 3G + Wi-Fi or 4G + Wi-Fi, potentially use it on carriers other than AT&T.
It’s important to know, though, that jailbreaking iPad can lead to problems with the device and Apple doesn’t provide tech support to jailbroken iPads. Proceed at your own risk. That said, the three iPad jaibreak programs I'm aware of are:
Once you've jailbroken the iPad, you may want to install non-App Store apps. A list of such apps compatible with the iPad is here.