I’m a contributor to the Autofac project and recently they switched their repository from Subversion to Mercurial which means I have to learn Mercurial. I’ve been working with it a little and the workflow process is… not quite as intuitive to me as Subversion, but then, it’s a pretty big mental shift and I’m still working on it.
These sites have helped me get up to speed and start understanding a bit better. Maybe they’ll help you, too:
Got other good ones? Leave ‘em in the comments!