I saw this today and found it very interesting: Hg Init: a Mercurial tutorial by Joel Spolsky.
There’s been talk at work about switching from Subversion to Mercurial, and this is a handy intro. Not that I am too troubled by Subversion; I know that it doesn’t help you as much as it could with merges… but then again until very recently we were stuck on a very old version at work.