I do have an experimental Ubuntu 10.04 (Lucid) image avalible from here - but keep in mind that Ubuntu Lucid is built on armv7, not armv6 - so this won't work on the N770/N800/N810, unfortunately..

Also keep in mind that this image is a bootstrap of alpha1, and there seems to be some serious bugs with apt/dpkg that make it almost unusable.

But I'll be uploading a refreshed image soon which should hopefully omit this issue.