The main ferry service for the island is The Steamship Authority. These boats run back and forth daily, with more frequent trips during Summer months. Boats embark from Woods Hole, MA. More information is available on their website
Another option is the Seastreak Fast Ferry – which departs from New Jersey/New York, and New Bedford, MA. This service is seasonal, so it is not always the best option
The airline serving the cape and islands is appropriately called Cape Air. They offer flights from various New England airports, including Boston Logan and Rhode Island’s T.F. Green airport. More information is available on their website.