I am preparing to build a Passagemaker dinghy in the Feb 25-29 class in Annapolis, and have been looking for a solution to lift the ~90 lb boat onto the roof of my minivan by myself. Inno and Rhino carriers look nice, but way too much $$ for my budget.
I found what looks like a great solution for building not only a car top carrier and loader, but also a nifty strap on dolly as well. Check it out here: http://www.pbase.com/onceagain/cartopper
This is the route I'm planning to go. Will come back and post pics and updates for those that are interested.