The Founders' Constitution: Chicago Edition

An excellent web resource from the University of Chicago Press and Liberty Fund:

In this unique anthology, Philip B. Kurland and Ralph Lerner draw on the writings of a wide array of people engaged in the problem of making popular government safe, steady, and accountable. The documents included range from the early seventeenth century to the 1830s, from the reflections of philosophers to popular pamphlets, from public debates in ratifying conventions to the private correspondence of the leading political actors of the day.

It comes complete with a wonderful table of contents, an incredibly thorough index, and a search engine. You can read more about it here.