Since launching DevMavens this week, I've had a few folks tell me they didn't previously know what a maven was.  The site shows some definitions, but the concept that led to my choosing that name is from the excellent book, The Tipping Point:

Mavens are one of the key players that Gladwell describes in this book about the way ideas are spread and certain products catch on.  Wikipedia has a summary of some of the book's ideas, one of which is The Law of the Few, which specifies three kinds of people important to the social success of an idea: Connectors, Mavens, and Salesmen. 

Mavens are "information specialists" or "people we rely upon to connect us with new information."  They accumulate knowledge, especially about the marketplace, and know how to share it with others. 

The idea behind the DevMavens group is to identify some (by no means is it an exhaustive list) of the Mavens in the Microsoft developer community, and help to further promote and support them.  There is an RSS feed on the DevMavens site, which is intentionally only brief introductions to the posts, since the idea is to drive traffic to the Mavens' blogs.  In addition, you can follow individuals' Twitter and eventually other social networking activities they choose to share via the site as well.