There are few things more aggravating than asking a client or opposing counsel for their availability and getting back something like “next Tuesday afternoon.” Part of my solution has been posting a free/busy calendar on my website, but I like the looks of Meet-O-Matic.
Like the best webapps, Meet-O-Matic is dead simple. No signup necessary. Just pick some dates, get the unique link, and email it to the people you need to meet with. They drop the dates they are not available, and you can check back to see what dates and times work for everyone.
Meet-O-Matic is a Simple Meeting Date Picker | Lifehacker