The company's teaser page still says "coming soon," but eagle-eyed reader Jason spotted the free Zipcar app [iTunes link] in the store today. We've been waiting for this app for quite a while, and it's exciting to see it in action.

The app provides Zipcar members with a location-based search for nearby Zipcar locations, allowing them to drill down to the individual garages via a map view. Reserving a car is as easy as clicking one big green button, and the app allows you to sort available cars by time, type and model to make it easier to find the one you want. You can see your upcoming reservations and cancel a car if you don't need it after all.

Once you get to your car, you can use the virtual keyfob to help find it in the garage by honking the horn (nice touch); while you still need to use your RFID-equipped Zipcard to activate the car's remote unlock and ignition system, once you do that at the beginning of your reservation you can put it back in your wallet and use the iPhone to lock and unlock the car. You can also extend your reservation from the iPhone app, as long as there's open time after your slot ends.

One somewhat quirky thing about the app is that there's no way to adjust your reservation time window except at the 'top' of the car search process; often as not, with the Zipcar website, you may find yourself tweaking the hours of your booking to improve your chances of finding the car you need. The lack of flexibility is noted on the app's iTunes page under "Coming Soon," so a future release will probably improve matters here. The Zipcar app requires iPhone OS 3.0 and works on the iPod touch as well, although most features will require a network connection.

Zipcar members are almost as enthusiastic about the service as iPhone owners are about their devices, so this combination is sure to strike sparks. Once you've got the Zipcar app downloaded, let us know your road trip experiences via the comments below.

If you're a car-free urbanite you've probably seen mention of Zipcar, or noticed one of their branded vehicles out and about. The company offers hourly rental automobiles with a rapid-deployment twist: there's no check-in or checkout process beyond reserving the time online and then swiping your membership card to unlock the car. The vehicles even include gas cards so you can fill up for free while you're on the road. Members are mostly enthusiastic about the convenience and ease of the service; soon, of course, there'll be an app for that.

Zipcar's newsletter and website have announced that the company's iPhone app will be coming soon, and the landing page offers an email signup to be notified when it ships. The promised feature set is a bit lean at the moment, but intriguing: find and reserve cars from the phone, plus the ability to unlock or lock the car from the app. Since the current Zipcar membership cards use RFID chips for the lock sensor, it's not quite clear how the app will accomplish the same trick -- GPS geolocation combined with a secure server connection? Wi-Fi or Bluetooth to the car's sensor? Can't wait to find out.