If you own your own personal boat for pleasure, you don't need a license. If you plan on renting a sailboat, just about all of them will require you have some sort of safe boating certificate or go through their boating fundamental course.

The requirements vary depending on what type/size of boat you're sailing, but virtually every boat will need a Fire extinguisher, Visual Distress Signals, marine sanitaion device, personal flotation devices, boat registration / documentation, as well as a host of recommended equipment.

Your best bet on getting all your questions answered is to contact the local U.S. Coast Guard MSO office, or either the U.S. Coast Guard Auxiliary or U.S. Power Squadron flotillas. Those guys live for answering these sort of questions, and also offer a host of boating classes.

http://www.SafetySeal.net

http://www.uscgaux.org

http://www.usps.org