OK, I don't really know how cool it is because I only just saw it for the first time last night and I haven't tried it. But it looks cool, and it has a cool website, and I want it to be successful. It's called Capital Bikeshare.
I know I cut off the prices - $5 for a day and $15 for five days.
There are 110 stations in DC and Arlington with 1100 bikes.
The website shows all the stations and you can click on a station and see how many bikes and empty slots are available at any given time - so you can plan where to get or drop off a bike. You can read the blog in 42 different languages, like Hungarian for Ropi or Spanish for Tomás, though they cold do fine with the English.
Here's their video explaining how it works.