The Commentary on the Mishnah has not been translated into English in its entirety. However, there are translations of Maimonides' introduction to Pirqe Aboth called "The Eight Chapters." English translation of Eight Chapters, Introduction to Commentary on Avoth by Joseph Isaac Gorfinkle, New York: Columbia UP, 1912.
The Mishneh Torah is published in the Yale Judaica series as a 14 volume set entitled The Code of Maimonides. A good place to start is with the second volume, which has been recently re-translated by Menachem Kellner, a noted scholar of Maimonides. Each Volume is listed individually under the category of the "Mishneh Torah".
Recommended translation: The Guide of the Perplexed. Translated with an introduction and notes by Shlomo Pines.With an introductory essay by Leo Strauss. Chicago: University of Chicago Press, 1963. Originally composed in Arabic, in 1190.