When your cock is completely limp, slap that bitch in the palm of your hand, close your fist around it, and pull it up towards your stomach. Your balls will then hang down from the bottom of your closed fist like a big ol' sack of money. Spread your legs, snap a picture, and send it to a an online hottie. She'll get so wet that she'll spread her nasty beef curtains and send you a picture back.
The money sack works best with pathetically short dicks, as it is easier to fit the entire dong in your hand (this is crucial). Also note that the stretchier your nuts, the better the money sack. The lower the money sack hangs, the more effective the results will be.
The money sack is also used as currency, so you can use it as payment for things like Craigslist ads, eBay listings, or your federal taxes.
Jim: "I just got done doing my taxes."
Nate: "Nice. How much are you getting back?"
Jim: "None. I owe the fuckers another twenty bucks."
Nate: "That sucks, man."
Jim: "I know. Now I'm going to have to send the bastards a money sack."
Craig: "Check out this chick I'm chatting with. She is smokin' fucking hot."
Mike: "Wow, you aren't kidding. She send you any nudes?"
Craig: "Not yet. I'm trying to get some."
Mike: "Dude, money sack that bitch. Works every time."