Canonical has just released the Ubuntu 7.10 Desktop Course. It is available from the release notes available at:
The course consists of a 398 page student guide and an even longer instructor's guide. I've only thumbed through it but it seems pretty thorough and good. Most of the info would also be applicable to Mint.
The work is release under a Creative Commons attribution-noncommercial-share alike license, which means if someone had they time they could modify the book for Mint.
This may be just the thing for those who are only recently beginning their GNU/Linux journey...definitely worth taking a look at.