I’m been using the Zipcar car-sharing service for almost a year now and still love it. It’s great for someone like me that lives downtown, doesn’t own a car, and needs a car every-now-and-again to run out to Ikea or somewhere. Not to mention, it’s great to show a history of car insurance so my rates are lower when I do get a car 
Anyhow, today Zipcar emailed all their customers with a link to a demo of their new interface that launches tomorrow. Firstly, I’m really impressed that they are organized enough to put together a whole walkthrough of their new interface (though I’m sure it’ll probably find its way onto the new site somewhere). But secondly, I think the interface is a substantial upgrade to an interface that was already “okay,” and miles above their competition.
Old interface:
The old interface was basically just a calendar “scrubber”/timeline that showed you when the cars in your area were free, after which you would use somewhat-annoying drop-down boxes to select the specific time you would like to book.
New interface:
The new interface is built around a search that let’s you browse a map of the cars in your area during the time you specify, then reserve the car right from inside the (Google) map.
You can also browse the listings of all the cars available, with the time you specified highlighted (the green bar in the screenshot below). Then, you can drag the time-window forward-and-back, and expand it to cover more time, via an Ajaxy scrubber that displays how much the trip will cost.
The improvements they’ve made look great, and I wish them luck in their roll-out 
This is a great example of how to roll out a major upgrade. Let your customers know ahead of time, make them excited about it, and convince them that it’s an improvement. It’s also a sign of how “Web 2.0″ can significantly improve the online user-experience with very simple enhancements. You have to wonder if Zipcar is growing faster than Hertz and Enterprise precisely because their online interface is so much better