After discovering this site back in November of last year I suddenly wished I was a New York socialite with black tie affairs crowding my date book. Mind you, I’m not a huge fan of parties so I’ve never wished that in my life.
Renttherunway.com is perfect for you if you’ve got a date book full of fancy affairs or even if you have several events in one month where you can’t show up in a re-heated dress.
How it works:
You must first enter your name on their waiting list. I did this and a couple weeks later I was accepted (so do it now if you think you might need it later on). Then you go searching. You can search by occasion, color, price, designer, body type, neckline, and sleeves.  Next you enter the date that you need it and once you’ve found the right dress they send it to you and you pay WAY less then what the dress would actually cost (there’s a Diane von Furstenberg that retails for $365 that you can cruise around in for a mere 50 bucks!)
Once you’re finished you simply ship it back to them-no dry cleaning necessary.
They also have packages available where you can pay to rent unlimited dresses for a season. Like I said before, if I were a New York socialite it would be totally worth it.

PS: They’ve recently added jewelry to their arsenal so now you can frost yourself with jewels that cost more than rent for less then dinner!