Ubuntu made it's mark in the Linux world many years ago with a robust desktop interface that could bridge the gap for users not used to a command line based OS, and has just announced they are also forging ahead with a tablet OS soon to be released to developers at the Mobile World Congress this year!
They are already creating a buzz with talks of high-end multitasking ability, using apps to collaborate seamlessly with others, a more secure mobile experience, and instant launch feature, and more. I admit, it looks really awesome and I can't wait to get our hands on a device with it loaded up to take it for a test drive!
The good news for developers is it looks easy to get an app in their app store as well, you can get developer information on the Ubuntu website. There is HTML5 options, Android Java options, and Native C++ type options if you want to get really down and dirty with developing something grand on Ubuntu.