Travel Technology - Cheap conference calling providers?

Anyone have any good ideas for a cheap - but reliable - conference call provider?

- All participants are domestic US.
- Call size is usually 8-10, max of 15.
- Features like operator assist, logging, recording, etc. are not needed. (I'm sure some people use them but in many years I never have even once.)
- Needs to be a toll-free dial-in from a traditional phone. I can't assume that many or any of the participants will be able to use VoIP.
- I can pay a monthly invoice or via CC.
- Typical usage would be about two one-hour calls per week.

I've had good luck with BT Conferencing (http://btbasic.com/)

We use Intercall and Premier, with the latter being cheaper. No problems with either.

In a pinch a few years ago I signed up with Budget Conferencing:

http://www.budgetconferencing.com

Service has been great and the price is right. And don't worry, the 800# does not say "Budget Conferencing" when participants call in. :)