JetBlue TrueBlue members who are first-time members of Zipcar can earn 500 TrueBlue points (1,000 points for Mosaic members) and $50 free driving credit. To qualify for the offer, TrueBlue members must pay a $25 one-time application fee and the $60 annual membership fee. Zipcar membership provides 24-hour access to vehicles in cities and airports around the world, by the hour or by the day. All vehicle rentals include gas and insurance.
You must apply for membership through the promotional link http://www.zipcar.com/partners/jetblue and enter your TrueBlue number at time of application to receive TrueBlue points. A TrueBlue membership number may not be added retroactively to any new Zipcar membership. For more information, visit http://www.insideflyer.com/link/?11428
Bottom line: Coupons are valid for 30 days from membership application and expire automatically so be sure to use your $50 credit as soon as you receive it.