As a student of the Martial Arts I definitely second the opinion that you should/could check out some classes in any martial art that does alot of throws and rolls. Brazilian Jiu-Jitsu, Aikido, Aiki-jutsu or Judo would all be choice options.

Edit... I realize that my addition of named arts gets you no-where....

As for falling? The best thing you can do is train your body to curl up rather than splay out. Our natural reaction when falling (which may or may not have something to do with our late great ancestors having grown up in trees) is to throw our limbs out to catch hold of something, anything, that will stop our fall (perhaps a precipitous one from the top of a ginko tree where we have, until recently, been eating/fornicating/napping/grooming). This is a BAD idea. Splaying out, especially while on a bicycle does things like put arms and legs in car-roll-over territory (etc). Unless you're on a mountain side and need to deploy your climbing axe the best thing you can do is to get as few of your limbs sticking out as possible and allow yourself to bounce.