We bring our own snorkel gear so that we don't have to share with anyone else and to make sure it fits but gear is provided for the snorkeling trips. Some people bring their own mask and snorkel then use the Club Med fins as a reasonable compromise.
Don't bring towels... you get the beach towel/card and you can get a fresh/dry towel as often as you want. We actually got two towels/cards per person on our last visit (Oct.) but I don;t know if this is a "normal" thing now or some kind of exception.
WiFi is available in the village for e fee on various schedules. Something like $50 for the week, $7 for a day, or $5.00 by the hour. Hourly is actual connect time which works well for checking email, not so good for 'surfing'. The last 3 years I've been able to get reasonable WiFi signal in our rooms but some visitors have to go to the village center to get a signal.
Not a lot of souvenirs to be had. Some people like to bring back a Conch shell but they take up a lot of space and you should make sure you get a "legal" one and that it has been cleaned very well.
Two things that you should make sure you bring: Insect repellent (they may or may not be bad, but best to be prepared) and Sun block (about twice as much as you think you will need.)
Edited: 1:27 pm, November 18, 2012