If you arrive by ferry, the Steamship Authority ferries have a good Vineyard Visitor publication that really tells you most of what you need -- including basics like beaches and biking trails, plus ads for good restaurants and even timely events for what's happing in the coming week or two.  Definitely pick one up.

Also, commercial tourist maps are available at just about every store in town so don't feel like you need to send away for elaborate information before you arrive.  You've seen these in plenty of resort towns.  Yes, they feature advertisers prominenty on the map, and the sketch is not always to scale but, in Edgartown, it's pretty much all you need.  Most of the local advertisers are quality establishments that you're likely to use/need anyway, and the town is small enough (or at least the shoppoing/tourist zone is small enough) that it's convenient and easy to get the map when you arrive.

Biking maps are also available and, although some stores may now charge for them, you may be able to get one for free or at a discount with your bike rental.  These are invaluable beyond any of the free maps and worthwhile if you plan to do any aggressive island exploration.  On the other hand, if you're just riding from Edgartown to Oak Bluffs or out to one of the beaches, a basic free map will be more than adequate.

Edgartown Board of Trade recently put out a glossy map and historic overview.  Look for those in stores as well, it appear to be new in 2006.  It lists antiques, art galleries, banks, beauty salons and spas, bookstores and newspapers, churches, hotels and inns, jewelers, recreation, restaurants, transportation information and trades & professional services in addition to retailers for clothing, florists, gifts, seafood & specialty food, hardware, home furnishings, photo services and sweets.  There's also a calendar of major events throughout the summer and fall (June - December) plus a brief history.  Whew.

Links to off-site resources:

Edgartown Board of Trade * P.O. Box 5134 * Edgartown, MA 02539