Isla de la Juventud
Isla de la Juventud is an island in Cuba.
 is a good source. Travel info outdated as of 2006-09, though.
Victoria,  is the local periodical.
Flora and fauna
Only two possibilities:
The prices are going to change in 2007-01/02, increasing from 20' pesos to 90 something. Reservations are imperative, with at least 5 days in advance. Nota: most Internet sources are outdated, Aerotaxi doesn't fly to Isla de la Juventud anymore.
Bus from Ciudad de La Habana (Estación Central de Ómnibus) to Batabanó (Habana province, south of the capital): 5 CUP for everybody (Astro bus). Go to the small ticket office of the NCC company (hard to find, better ask where it is) in the Estación Central de Ómnibus. You get a reservation for Batabanó (if you pay in CUC, you'll have reserved places so you this reservation is a guarantee to leave) plus a ticket for a right to go on the bus (you pay inside). I'm not sure about the bus leaving hours, but they seem to be in the morning (09:00-12:00?).
The boat ("Kometa" catamaran) costs 50 pesos per person (25 for children of less than 12 years of age):
No reservations needed to go to the island. Best to buy a ticket with one day in advance for the return (or you'll have to wake up at 5 A.M. to leave at 12 A.M.). 1 to 2 boats daily, excepts on Sundays. The trip isn't a experience per se (modern, long, highly cooled air, can't go on deck...). No bicycle can be brought on the island. Knifes and the such must be checked in (free, secure and minimal loss of time).
An old Lada with a driver will cost you 35-40 CUC a day. There are only 2 official car taxis on the island, the rest are bicitaxis. You can also rent a bicycle by the hour or the day.
 seems to be rich in info.
Nice 20 min hike to the hills that oversee Nueva Gerona. Physical but nice. Ask for directions to get to the base of a hill (near "la Cueva del Agua") then just go up following trails when you find them. The base of the hill is filled with rubbish heaps but the top and the middle are nearly pristine.
No security problems whatsoever on the island as long as you avoid the military zones.
Important warning on sex:
In Nueva Gerona:
Movie theatre on the plaza (600 places, almost always nearly empty, 2 CUP).