Innocentive

InnoCentive serves as a crowd-sourcing R&D broker. Companies can post R&D challenges to their site and 90,000 independent researchers in 175 countries have an opportunity to tackle them. Interestingly, many of the solutions come from "left field": physicists who easily solve what are nominally difficult chemistry problems, for example. Rewards range from $25,000 to $1 million, which works out pretty cheap given that American firms spend around $200 billion on R&D annually.

See also: The Rise and Fall of Corporate R&D, The Economist.