A friend turned me on to Doodle for distributed meeting scheduling. Four steps to a url you can send out to an unlimited number of people. You select dates and times.
Anyone who has the URL can then, without logging in, vote for a date/time that works for them.
There are other options available, but this is enough to set up the occasional lunch with busy friends, which is what I use it for.
If you need to do any scheduling of multiple parties, give Doodle a try.