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.
Taxing and Spending Clause
To date, the Hamiltonian view of the General Welfare Clause predominates in case law. Historically, however, the Anti-Federalists were wary of such an interpretation of this power during the ratification debates in the 1780s. Due to the objections raised by the Anti-Federalists, Madison was prompted to author his contributions to "The Federalist Papers", attempting to quell the Anti-Federalists' fears of any such abuse by the proposed national government and to counter Anti-Federalist arguments against the Constitution.