PG Dive website has a nice map and brief explanation of most of the dive sites on Cape Ann. CAD website has same thing. PG also runs a guided shore dive on the weekends during the summer. Other area clubs and shops do the same thing. IMHO, dive either Folly Cove, OGB or Pebble Beach for starters. All have relatively easy entry/exits, have pretty good parking situations(as far as CA goes) and you might be able to get a few lobsters. Also, try Front or Back Beach for ease of parking/entry/exit, but probably no bugs. Good luck.
LobstaMan