This book constitutes the thoroughly refereed post-conference proceedings of the Third International Workshop on Resource Discovery, RED 2010, held in Paris, France, in November 2010. The 13 revised full papers - from 24 initial submissions - were carefully selected during a second round of reviewing and improvement from the lectures given at the workshop and are presented in extended version in the book. They deal with the following topics, resource discovery for composition, bioinformatics resource discovery, textual resource discovery, and web service discovery.