Android tablets may be Linux-based, but if you're more interested in Ubuntu then a new Chinese slate from TENQ might satisfy instead. The TENQ P07 has been spotted over at Gizchina, and reportedly runs Ubuntu Netbook Edition 10.10 "Maverick Meerkat" on a 1.6GHz Intel Atom processor with 2GB of RAM and a 32GB SSD.
The OS supports multitouch and, since it's the netbook edition, will have chunky, finger-friendly buttons making it somewhat more suited to tablet use. Unfortunately, that Atom processor probably means battery life won't be stellar, though instant-on is rumored. There's obviously a hunger out there for Ubuntu tablets: there's already been a project to get the OS running on Samsung's Galaxy Tab.