If you are planning a holiday your first step should be to check out the TravAbility website.  Whether its a cruise or a trip to Melbourne, New Zealand, London or Vancouver you will find lots of really valuable and up to date on this website.   There is even information about accessible wheelchair taxi services in Brazil.

Information on the site includes photographs taken on board cruise ships, with detailed, accurate information about accessibility.  Even if you are not planning a holiday it makes for interesting reading.