The Ubuntu Touch Developer Preview has been released. For the time being it is aimed for developers therefore it isn't something you should use in daily basis. Several features are missing such as playing music, no mobile data connection, PIN/PUK support, etc., and of course there are bugs.
For now the supported phones and tablets are Galaxy Nexus, Nexus 4, 7 and 10.
Detailed instructions on how to install Ubuntu Touch Developer Preview on your device along with a PPA which supports Ubuntu Precise, Quantal and Raring can be found in https://wiki.ubuntu.com/Touch/Install