There's an appealingly straightforward article in the SF Chronicle today about the pros and cons of the various different methods out there of preserving open bottles of wine. My own preferred method, which is not worrying about it & simply seeing what the wine tastes like the next day—an approach somewhere between rigorous scientific inquiry and absolute laziness—is partly predicated on the fact that, as a wine editor, I've got so much wine around I don't know what to do with the stuff anyway. (I mean, I know to drink it, but you get the point.)
Though the Chronicle article's author, Janet Fletcher, didn't conduct any rigorous testing of her own, apparently*, she does pull in some useful scientific commentary from professors at UC Davis and Purdue, along with thoughts from various Master Sommeliers, Masters of Wine, Elder High Wizards of Grapeomancy and whatnot. She comes to the conclusion that, generally speaking, you're kind of out of luck regardless of which method you use, in that your wine is going to oxidize to some degree no matter what. On the other hand, with young reds, a little oxygen can be a good thing—which is why decanting them isn't a bad idea either.
My advice? Skip the pumps and sprays and whatnot. Drink what you want the first day, stick the remainder in the fridge (red or white), see what it's like the second (most likely still good, if different), and plan to cook coq au vin or brasato al barolo or what have you after that. Or else just make sure to invite enough friends over; wine is more fun with more people around anyway, and less fun when you worry about it overmuch.
*One has to love the speed of information dispersal these days. I heard from Janet Fletcher about half an hour after I posted this, who politely pointed out that she in fact did do a controlled tasting with a number of wine professionals in her research for the article, blending bottles to eliminate bottle variation and tasting blind. The results? As she put it, "resoundingly inconclusive"—hence her decision not to include the tasting in the article. Not to mention a good reason to be skeptical of any of these wine preservation methods that require you to dig into your wallet.