Online scheduling tool . Time for RPGs

Does anyone know of any good online tool usable for scheduling several people?

I need some sort of help in finding times when all members of our gaming group can get together and play (RPGs and miniatures games).

We used to to it via e-mail which can get messy rather quickly as you wont know who is saying yes or no to what as the replies bounce back and forth. Then things would start to get off topic …
Those in the group who only checked their mail once per day would complain about having to wade through a ton of messages.

Now we have started our own forum which is better, since we can have separate threads for finding game times and others for general chatter. This works better, but if anyone knows of some kind of online thingie that helps I would appreciate the help.

Any other tips for getting a group of busy gamers together for some hack and slash is also appreciated of course.