Travelers Doctor offers a wealth of information about what you should be prepared for on next visit as well as precautions to take.
Vaccination Information is provided for all world countries by the U.S. center for disease control.
Travel Health: One of the best sites on the net to discover a wealth of information about staying healthy worldwide. Registration free but required.
Travel Medicine Program: Offered by the Canadian government this is a great site to find the latest developments for worldwide travel.
Who: The World Health Organization provides up to date information about outbreaks of disease in third world countries.
MASTA: this is an Australian site with a wealth of information about traveling abroad including extensive bulletin boards where you may post any question you may have.
Travel Warnings: This searchable database will bring you the most recent travel warnings and advise from the Australian, British and US governments as well as a very useful travel guide.
Travel Insurance offerings from a host of major providers is available at this site.