My daughter is a vet and I recently asked her about sailing in the Caribbean with a dog. She referred me to two sites:
Look on the left sidebar for "Directory" then click on Pet Immigration and Quarantine Rules. This takes you to a page where you can select a country of interest and get a summary of their rules.
Alternatively, try http://www.aphis.usda.gov/vs/ncie/iregs/animals/#S
This site is used by vets and deals with "exporting animals" (not just pets) from the US to other countries. As it's US specific it may not be all that helpful, but I did find that on the pages for some countries there are references to dogs and cats and links to the foreign governments rules.
You should probably consult a vet at least six months before you go as some countries require two tests for rabies vaccine antibodies at intervals of several months. Also, many countries now require that a 'chip' be implanted in the pets neck so that the animal can be easily identified as the one referenced in any documents you may carry concerning the pet's health and vaccinations.
Hope that helps.