WebMD advises drinking lots of water the morning after, to combat the dehydration caused by excessive boozing. Other possible options include consuming burnt toast and drinking sports drinks with electrolytes (Ed. If you don't want the sugar, I suggest something like Smart Water instead). A couple of pain-relief pills should help with the inevitable headache (though other sources warn against taking aspirin, naproxen sodium, or acetaminophen while alcohol's still in your system).
eHow seconds the re-hydration recommendation, adding that a BRAT diet the morning after comprises mild foods your stomach should be able to tolerate (Bananas, Rice, Applesause, Toast).
Men's Fitness recommends eating eggs but avoiding coffee, as caffeine serves to dehydrate you further. (Ed. Though perhaps drinking twice as much water as coffee may negate this effect? The caffeine can help take the edge off your headache, just sayin'.)
Real Simple also hops on the toast/sports drinks wagon, but tosses out the surprising suggestion of eating spicy foods which "distracts your body from focusing on your hangover." (Ed. Yeah, I'll just bet.) And apparently, the extract of prickly pear may reduce nausea. (Ed. Who knew?)
I suppose, as a last (or first) resort, you can give products like Hangover Helper a try, though I can't personally vouch for it, or any's, efficacy.
Probably the best thing you can do for yourself is eat like you're just getting over a stomach bug and get as much rest as you possibly can. And next time you go out boozing, be sure you've filled your stomach with a good dinner beforehand and pace yourself, damn it. What are you, just out of college?
(Ed. Ignore me; I'm just snippy 'cause I haven't had a drink since August 2012 and God knows I coulda used several!)