Cruising Medical Insurance
Most health care outside of the US is inexpensive compared to US rates so many cruisers have opted for high deductibles or major medical only. Be sure the policy includes air ambulance for air lifting you out of possibly remote areas or getting you to a major medical facility if necessary. One company you might want to check with if you plan on being outside the US more than 6 months in any one calendar year is Global Medical (www.globalmedicalinsurance.com).
Also, see William Mahaffy''s article, Health Insurance while Cruising: http://www.sailnet.com/collections/articles/index.cfm?articleid=mahaff020