Try signing up for crew with the Cruising Rally Association. They run the Carib 1500, Atlantic Cup, and other rallys. They post a crew list for volunteer crew for boats partcipating in these rallys. In general, you would be responsible for your own transportaion to the boat and back home but there would be no costs to you during the Rally itself. You can find the crew signup form at
http://www.carib1500.com/. No experience is needed and these Rallys are a good way to get off-shore experience and also evaluate boats.