OpeniBoot brings Android to iPad, iPhone 4, and iPod Touch
OpeniBoot is the successor to Bootlace, which ported the Android OS to the iPhone 2G and 3G. This new iteration will support the newer generation of Apple devices, including the iPad, iPhone 3GS, iPhone 4, and the 2nd-generation iPod Touch. See below for a video of OpeniBoot loading on an iPad.
If you're unfamiliar with such programs, all you need to know is that they are open source implementation programs that allow your iOS device to load an unsigned kernel, like Android, to your device. Once you have loaded such a program, you will still have the option to load the original OS. It basically makes your iOS device like a dual-booting computer. OpeniBoot isn't yet available for your newer iOS devices, but judging from the video, it should be along shortly.
source: iDroid Project via Redmond Pie