Rent the Runway is a brand-new invitation-only site that lets you rent designer dresses for a fraction of the price.  You’ll get to sport the latest fashions without draining your bank account; and in return, you treat the dress as if your best, most fashionable friend lent it to you.

In the age of Facebook, you really don’t want to be tagged in photos wearing the same dress to different events and how many of us can afford a closet of $600-$2000 dresses?  You’ll never again be tempted to commit one of the worst fashion sins: buying a dress you cannot afford to keep, tucking in the tag, wearing it and then returning it.

You can reserve dresses in advance, so you know that you’ll be able to wear that Robert Rodriguez dress to your friend’s wedding in two months.  Rent the Runway lets you rent 10 dresses for the price of owning one.  A decent exchange considering they also handle all of the dry-cleaning.  They even have stylists available by chat and phone!  Each dress is accompanied by a Fit Kit, which includes items like double sided tape and Braza magic clip bra strap converters.  With customer service like this, you not only get a designer dress but a luxury boutique experience.

Fear not full-figured fashionistas, though current stock of sizes over 10 is pretty small, Rent the Runway is currently expanding their selection of larger sizes.  If you rent a dress and it doesn’t fit, you can return it within 24 hours for a full refund of the rental price.  If you are trying a designer for the first time, you can get two sizes of the same dress and you can rent a backup dress for only $25 with any other rental.

They are constantly expanding their selection of available designers, including the addition of Matthew Williamson and Vena Cava in January 2010.  Right now, you can rent gorgeous dresses by Lela Rose and Project Runway alum Christian Siriano.  Rent The Runway will also be offering accessories by the end of spring 2010 so that you can create and rent an entire look.

All that’s left to decide is if you’ll share your secret with your friends or credit your amazing wardrobe to some super stock picks!

Four day rentals begin at $50 and top out at $200, with many options at every price point.

Bonus: Use the code INSTYLEFREE to rent one dress and get another free!