The North Sound Express Ferries leave from Trellis Bay, with published fares & schedules (see contact info below). I caught the fast ferry to Virgin Gorda (and it is FAST!). This one makes stops at the Spanish Town dock (called "the Valley" by locals & on the schedules), and then continues on to Leverick Bay & Bitter End Yacht Club.
They prefer reservations, so please make sure you call or have your hotel take care of it for you!
NOTE: Most other ferries for getting around in the BVI's or over to the USVI's leave from RaodTown on Tortola. However, the free Marina Cay shuttle also leaves from Trellis Bay on Beef Island. The exclusive Little Dix Bay shuttle also picks up at Trellis Bay (free for resort guests).
There is a free shuttle from the main Beef Island airport to Trellis Bay. Just ask the airport employees, and they'll make sure you get on the right shuttle. Another leaves for Road Town Harbour, but I'm not sure if that one was free or not.