There are few things more frustrating than trying to schedule a meeting via email. You all probably know what that's like. I now force people to use a Doodle to indicate their availability in a central location. I've found that most people are familiar with Doodle or they figure it out pretty easily. Of course, the ideal situation is when everyone keeps their schedule up to date in Outlook, but not everyone uses it and I often have to schedule meetings with people outside of UWEC, so Doodle really helps.
Did you know you can also use Doodle as a sign up sheet? When you are done setting the times and days, there is a settings area that is collapsed by default. Click the arrow to show the settings (see the screenshot below). You can limit it so participants can only choose one option and then limit it so that only one person (or however many you want) can choose each option. A faculty member is going to use Doodle to schedule students to meet with her. I also used it to schedule interviews for student workers.
I also like the "yes-no-ifneedbe" option so that when you're doing a regular Doodle to schedule a meeting, people can indicate that they could attend if need be, but would prefer a different time.