Game scheduling tool?

At work, I’ve used web apps to schedule meetings between a bunch of people with busy schedules, but it never occurred to me to use such things to schedule a game. I know some campaigns out there (I’m in one at the moment) don’t have a set meeting time – the players get together when they can. Often, though, these games fall apart for lack of meeting. For these sorts of scheduling issues, a web application might be useful. There are a bunch of these – one of them was mentioned today on Lifehacker (which is what inspired this post).