We all owe a great debt to Poggio Bracciolini, who in the early 15th century hunted down and recovered so many classical texts. His letters have never been published in English, aside from an unsatisfactory collection to his friend Niccolo Niccoli, whose massive collection of Greek and Latin manuscripts forms the kernel of the Biblioteca Mediceo-Laurenziana in Florence.
Harvard University Press have launched a series modelled on the Loeb Classical Library for renaissance writers. Details about it are here.
UPDATE (2012): Updated link for the I Tatti library here.