Here is a short video introduction to DVCS: http://youtu.be/1BbK9o5fQD4.
Note that the Fogcreek Kiln Harmony feature now allows seamless work between Git and Mercurial with the same Kiln repository: http://blog.fogcreek.com/kiln-harmony-internals-the-basics/.