Crafty is a state-of-the-art computer chess program, and uses all of the search algorithms you have probably read about, negascout search, killer/history move ordering, SEE (Static Exchange Evaluation) quiescence move ordering and pruning, hash (transposition/refutation) tables as well as evaluation caches, selective extensions, recursive null-move search, and a host of other features that have been used and are still being used in most computer chess programs. If it's not in Crafty, either it is on the "to do" list, or it has been tried, found wanting, and discarded.

License: free