Congratulations! You get an extra week off!

The bad news? It's next week!

OK, so that's not exactly a common scenario -- though it did happen to a friend of mine not long ago. More commonly, your long-reserved vacation week just kind of sneaks up on you. You like the idea of travel and dream of planning an interesting trip, but work gets overwhelming, and you get busy, and you just never get around to buying tickets. So you end up spending your summer vacation at your mom's house, painting the porch.

While it's always good to make your mom happy, such a "vacation" isn't exactly the stuff of dreams for most of us. Fortunately, we live in the 21st century, where some dreams are easy to realize. We might not have flying cars yet, but an affordable, fun last-minute vacation is only a few mouse clicks away.

Scoping your options
First of all, even vacation options that "always sell out months in advance" often don't -- or at the very least, frequently get a few last-minute cancellations. Here in New England, for example, it's a truism that you can't find a decent rental house on Nantucket or Martha's Vineyard if you wait until after April to make your reservation.

But with one minute of work, I just now found several nice (and relatively affordable) Nantucket rentals available next week or the week after, thanks to Nantucket Real Estate's website. If you've been pining for some time in your favorite seaside, lakefront, or mountain resort area, contact rental agents and see what they've got. Odds are, you'll be pleasantly surprised.

Craving airline food?
If more elaborate travel is your thing, last-minute planning is just as easy. In fact, there's a whole corner of the travel industry set up to accommodate last-minute vacation planners. Start with, which offers pre-constructed packages to hundreds of interesting destinations. If you don't have a specific spot in mind, they can help you brainstorm, with simple-to-use searches organized around "themes" such as International, Sun & Beach, Food & Wine, or Casino, among others.

One caveat: The best pricing usually takes advantage of off-day airfares. If you have some flexibility around your days off, traveling on an odd schedule -- Wednesday to Tuesday, for example -- could save you hundreds of dollars over a more typical Saturday-to-Saturday round trip. If you don't find what you're looking for at, surf over to (NASDAQ:EXPE) and check out the deals page, which almost always has some interesting special offers from hotels and resorts looking to fill rooms.

That "DING" thing
Need some more ideas? The airlines sometimes have special last-minute deals available directly via their websites, and one of them might help spark your planning.

If you have a little bit of time to plan -- at least a couple of days -- try downloading Southwest's (NYSE:LUV) famous/notorious "DING" tool, which brings deeply discounted last-minute offers right to your desktop. The graphics are silly, and the "ding" sound might drive you nuts, but the discounts are often very large. And since Southwest doesn't participate in sites like Expedia or Orbitz -- or book through third parties at all, for that matter -- DING is the only way to find out about them. Not all of the DING deals are last-minute options, but some are -- and one might be just right for you.

Help fund that last minute vacation with some terrific money-saving ideas from the Motley Fool's Green Light newsletter. Green Light co-editors Dayana Yochim and Shannon Zimmerman offer hundreds of dollars' worth of money-saving ideas every month, together with helpful articles on investing and improving your financial picture and a friendly members-only discussion board for your ideas and questions. A 30-day all-access free pass is yours for the asking.

Fool contributor John Rosevear, whose favorite summer escape location is a friend's house on Fishers Island, does not own any of the stocks mentioned above. The Fool's ever-clever disclosure policy prefers a dinghy to a ding.