http://www.njtransit.com/tm/tm_servlet.srv?hdnPageAction=SpTo
(Very bottom of the page)

I don't know when this expires, but Zipcar is offering $50 in free driving credits for new drivers when you use the promo code NJTRANSIT. You might need to sign up for the NJ market (hence YMMV) but you can reserve cars in any Zipcar area.

Please don't link directly to Zipcar. I know they deactivate referral codes that are posted, and although I don't think this counts, let's not risk ruining the deal.

Before signing up make sure you don't belong to an organization that offers a discounted sign-up fee, too. For instance, if you belong to the Freelancer's Union (free membership if you freelance) or have the AMEX IN:NYC card, you get it.

Schools, too, but way too many to list. Search Google for your college name on zipcar.com ex: (columbia site:zipcar.com )

Philadelphia people, if you click through to ZipCar's site, you can get a better offer from Zipcar.

$75 of Free Driving with code WEBPHILLY75

Someone might want to try different areas and see what kind of offers come up from zipcar themselves