Google made the source code of its Android platform available for free today, you can get it over here.
Android is not a single piece of hardware; it's a complete, end-to-end software platform that can be adapted to work on any number of hardware configurations. Everything is there, from the bootloader all the way up to the applications. And with an Android device already on the market, it has proven that it has what it takes to truly compete in the mobile arena.
Even if you're not planning to ship a mobile device any time soon, Android has a lot to offer. Interested in working on a speech-recognition library? Looking to do some research on virtual machines? Need an out-of-the-box embedded Linux solution? All of these pieces are available, right now, as part of the Android Open Source Project, along with graphics libraries, media codecs, and some of the best development tools I've ever worked with.
Have a great idea for a new feature? Add it! As an open source project, the best part is that anyone can contribute to Android and influence its direction. And if the platform becomes as ubiquitous as I hope it will, you may end up influencing the future of mobile devices as a whole.