I'm a Zipcar member for occasional use; it's one of the options that helps our family of four get along with a single car. Unfortunately, the closest Zipcars are 1-2 miles from my house, so I can't easily walk to get one. However, I can quickly bike to get one, which was what I did yesterday, when I needed to transport my daughter to her friend's pool (my wife had our car with her at her work).
I rode my bike to Ballston, locked my bike to the pole (see photo), picked up the Zipcar, "zipped" back home to get her, took her to her friend's, returned the car, biked home, realized I'd left my phone in the car, biked back, got the phone, biked home again. Okay, the last part was a bit of a pain, but I can only blame my own brain fart for that.
I've looked around on the web and haven't readily found other examples of how Arlington coordinates the bike parking with the carsharing. Note in the photo that I've locked my bike right to the Zipcar pole. The pole incorporates a bike rack directly into it. Now that is convenient. Good job.