Magothy Marina in Severna Park is one of the few liveaboard-friendly marinas I know of. I have been living there for the past 5 years.
Quiet (no boatyard, no tiki bar)
Thriving liveaboard community (a few weirdos, but mostly good folk
Easy access to Chessie
Friendly and helpful staff
Lots of summer parties/events
No tiki bar
A little more exposed from the east than I'd like.
All in all, it's a great liveaboard experience. Highly recommended!