Speek lets you very simply organize conference calls. The number is unlimited, but they say the quality begins to deteriorate after ten people. It’s free.
You quickly register and then you’re given a url address for your call. You email that out, people click on it and enter their number, and that Speek immediately calls them. It’s pretty easy. They say you can upload files to share, but that didn’t seem to be working for me. I suspect they’ll work out that kink quickly.
I’m adding it to The Best Online Tools For Real-Time Collaboration. By the way, I’ve just completely updated that list.