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.
Confederation Period
Ratification of the Constitution required the approval of nine states. The ratification debates in Massachusetts, New York, Pennsylvania, and Virginia were of particular importance, as they were the four largest and most powerful states in the nation. Those who advocated ratification took the name Federalists. To sway the closely divided New York legislature, Hamilton, Madison, and Jay anonymously published "The Federalist Papers", which became seminal documents that affected the debate in New York and other states. Opponents of the new constitution became known as Anti-Federalists. Though most Anti-Federalists acknowledged the need for changes to the Articles of Confederation, they feared the establishment of a powerful, and potentially tyrannical, central government. Members of both camps held wide ranges of views; for example, some Anti-Federalists like Luther Martin wanted only minor changes to the Articles of Confederation, while others such as George Mason favored a less powerful version of the federal government proposed by the Constitution. Federalists were strongest in eastern, urban counties, while Anti-Federalists tended to be stronger in rural areas. Each faction engaged in a spirited public campaign to shape the ratification debate, though the Federalists tended to be better financed and organized. Over time, the Federalists were able to convince many in the skeptical public of the merits of the new Constitution.