The main Web site of the Socotra Archipelago Conservation and Development Programme (www.socotraisland.org) has good background information.
Visas are required for American travelers; visit www.cdc.gov for information on recommended vaccinations and medications.
Although the U.S. State Department currently maintains a travel warning for Yemen, most experts agree that travelers need not have safety concerns about Socotra.
Organizing travel to Socotra is challenging, so a travel agent can be very helpful: try the excellent Poe Travel (800-727-1960; www.poetravel.com).