The Steamship Authority is probably the easiest way to get from the wharf of MA to either Martha's Vineyard or Nantucket. Wood's Hole has a decent amount of parking, but during the summer, you'll more than likely have to take a shuttle from the parking lot to the wharf. This is also the only way you can get your auto ferried over to the island. If you check their website, you can see how many cars are presently in the standby line and the approximate wait.
The ferry isn't anything special, but it gives you the option of outside standing room or interior seating. It takes the SA about 50 minutes to get you from Woods Hole to Vineyard Haven.