More and more parallel and distributed systems (cluster, grid and global computing) are both becoming available all over the world, and opening new perspectives for developers of a large range of applications including data mining, multimedia, and bio-computing. However, this very large potential of computing power remains largely unexploited this being, mainly due to the lack of adequate and efficient software tools for managing this resource. Scheduling theory is concerned with the optimal allocation of scarce resources to activities over time. Of obvious practical importance, it has been the subject of extensive research since the early 1950's and an impressive amount of literature now exists. The theory dealing with the design of algorithms dedicated to scheduling is much younger, but still has a significant history.