One of the felicities of the American calendar is that December 31 — the cutoff for giving tax-deductible contributions to charities — comes hard on the heels of December 25, a holiday that inspires generosity in many of us. Whether it is motivated by a desire to minimize tax bills, by religious inspiration, or simply by the warmth of the holiday season, the giving impulse is worth giving in to.

The down economy, after all, has a way of giving charities a one-two-three punch. For human services charities, the needs are greater, because more families are having a tough time making ends meet. For charities that rely on government funding for some of their operations, the tough local and state fiscal situations mean tightened budgets. And for all charities, donors have less money to give away than they did during the boom years. Crain’s New York Business reported this week that charitable gifts by some corporations are being slashed as much as 50%.

So give — but give wisely. Too many of this city’s universities are taking charitable money and pouring it into Middle Eastern studies departments dedicated to spreading anti-Israel and anti-American propaganda. Too many human services charities spend donor money paying lobbyists to advocate for a never-ending expansion of the welfare state. And too much charity money is spent on the expenses of fundraising — paying telemarketers and the bills for lavish benefit dinners. The attorney general of New York, Eliot Spitzer, yesterday released a useful report detailing some of these abuses; it’s available online at www.oag.state.ny.us/charities/pennies02/penintro.html. The tax returns of many charities, which even detail how much the groups’ executives are paid, are now available online at www.guidestar.org. Research aside, the best guarantee of a gift you won’t regret is to give time as well as money. If you can get involved as a volunteer or volunteer leader at a charity, you’ll be able to keep a close eye on whether your money is being put to good use. If it is, you may find that knowing that you’re helping make the city and the world a better place is the best holiday gift of all.