Voyagers in Time Author:Robert Silverberg (ed) A collection of time travel stories, including the most famous one by H.G. Wells, and those by other authors:P.Schuyler Miller, William Tenn, Lester Del Rey, Alfred Bester, Robert Silverberg, Poul Anderson, Larry Niven among others.
A great collection of classic SF (from the 50's and 60's) on Time Travel themes and alternative history. The story by Alfred Bester, "The Men who Murdered Mohammed", puts the question can we alter history?