The Caribbean airline LIAT has a couple of passes. If memory serves, one is for 7 or 10 days and the other is unlimited for a month. They are based in Antigua and fly to about 20 islands, including Sint Maarten. They also have some special LD fares that are lower than the normal fare, yet allow unlimited stopovers as long as you fly in a more or less straight line.
I did a t/s exchange to Sint Maarten a few years ago, and booked my tickets from the US openjawed, in to Sint Maarten and out of Antigua. I booked a LIAT ticket to close the jaws, flying Sint Maarten to Antigua with a free stopoever in St. Kitts enroute.
Unless a recent ownership change has led to a policy change, Air Jamaica also allows free stopovers enroute. I used them on another Caribbean trip for that purpose. I had an exchange in Barbados, and used Delta skymiles for a ticket on Air Jamaica. The itineray was Atlanta to Jamaica to St. Lucia to Barbados. I did a free stopover on St. Lucia on the way back for a few days and could have also done Jamaica if I had wanted to do so. The free stopovers are on both ff and paid tickets.
There are also some island hopping posibilities by boat. There is a fast ferry from Guadeloupe to Martinique, stopping some days at Dominica enroute. The scheduling works for a day trip from Guadeloupe to Dominica, which I did when I had a t/s exchange in Guadeloupe. If you were staying overnight, you can do all three islands.
From Sint Maarten / St. Martin, you can also do day trips by boat to Anguilla, St. Barths, and Saba.
The new EasyCruise also offers some interesting island hopping opportunities.
www.easycruise.com
