Original meaning
Originalists of all stripes cite "The Federalist Papers". It is fairly tenuous to suggest that this represents a good source for the original "intent": after all, Alexander Hamilton, who wrote the majority of those essays, was absent for the greater part of the Philadelphia Convention, and John Jay did not attend it at all. However, James Madison, the principal framer of the Constitution also wrote a substantial amount of "The Federalist Papers". Also, to suggest Hamilton and Jay's absence from the convention implies their ignorance as to the Constitution's original meaning is demeaning to those two men and inaccurate. The collected anti-Federalist papers, of course, will be no use at all to a person searching for the original "intent" of the framers. However, as evidence of how a reasonable person at the time would have understood the words of the Constitution, "The Federalist Papers" and the anti-Federalist essays are evidence of direct relevance.
The Federalist Papers
"Federalist No. 10" is generally regarded as the most important of the 85 articles from a philosophical perspective. In it, Madison discusses the means of preventing rule by majority faction and advocates a large, commercial republic. This is complemented by "Federalist No. 14", in which Madison takes the measure of the United States, declares it appropriate for an extended republic, and concludes with a memorable defense of the constitutional and political creativity of the Federal Convention. In "Federalist No. 84", Hamilton makes the case that there is no need to amend the Constitution by adding a Bill of Rights, insisting that the various provisions in the proposed Constitution protecting liberty amount to a "bill of rights". "Federalist No. 78", also written by Hamilton, lays the groundwork for the doctrine of judicial review by federal courts of federal legislation or executive acts. "Federalist No. 70" presents Hamilton's case for a one-man chief executive. In "Federalist No. 39", Madison presents the clearest exposition of what has come to be called "Federalism". In "Federalist No. 51", Madison distills arguments for checks and balances in an essay often quoted for its justification of government as "the greatest of all reflections on human nature."