Linux Mint 6 (Felicia) is the latest version and it is based on Ubuntu 8.10 (Intrepid Ibex). Linux Mint 7 will be based on Ubuntu 9.04 and is being worked on already by the Linux Mint developers. There are two versions of Linux Mint:

The Main Edition
The Universal Edition

The universal edition does not include any proprietary software, support for restricted formats, or patented technologies. It's geared for people in countries that might otherwise forbid some or all of these things.