The problem with NYC isn't finding what to do...it's more like knowing what not to do and letting everything else just find you. So many friends of mine come through NYC on tours or just for general vacations and their agenda is simple:
Statue of Liberty, Times Square, 5th Ave, Empire State Building, blah blah blah.
The thing is; I have seen all of these things. Landmarks are landmarks for a reason. They are popular because they have proven to be so appealing to the masses. I don't condemn my friends for wanting to see these attractions. But at the end of the night, everyone just wants a place to hang out and NOT pay $9 for a beer.
The best resource that a cheap alcoholic/party-goer in NYC can use is: MY OPEN BAR This site has likely turned hundreds, if not thousands, of early morning, Yoga class attending, NYU hipsters into hung over, not so health conscience anymore, mediocre students. Is that something to aspire to? You decide. Either way, the site shows you where the free booze is in NYC each night-and the free booze is typically accompanied by a cool party, gallery opening, or SOMEthing more than you'd find at the pub downtown back *home*.
RODEO BAR is simply always another favorite of mine. From 4-8, Sunday-Thursday, they have these GIANT frozen margaritas for $4. I don't care how much you drink; it'll only take you two to get fucked up. Not to mention the fact that the food is freakin' phenomenal. If you go...make sure you get the Cowboy Kisses. They're shrimp wrapped in jalapeno and bacon. The place is chill with a giant upstairs with couches where people hardly go. They also have sweet rockabilly and western bands in the evening-a genre most of NYC wouldn't touch with a stick-but it's awesome; trust me.
CHEAPSHOTS is also a great place for, of course, cheap shots-and other drinks. Thursday nights are Ladies night. That means you drink for half off, ladies. And if it's your birthday-you drink whatever you want for free all night long here.
Between that site and those two places..you shouldn't ever spend more than $5 on a drink in NYC. So don't!