This isn't quite the Hitchhikers Guide to the Universe but Hitchwiki does want to be your hitch-hiking guide to the Earth. Hitchwiki is a Google Maps based wiki that allows hitch-hikers to share good and bad hitching places.
If you are planning to hitch-hike anywhere you should check out Hitchwiki before setting out to find the best places to get lifts. Good hitching locations are shown on the map with thumb icons. If you click on an icon you can dicover the spot's rating and a brief description.
Using the 'Add Place' tab anyone can share their favourite hitchiking spots on Hitchwiki. You just need to click on the location of your spot on the map, rate the location and provide a short description.