Conference telephones on plain old telephone lines
US Robotics

Conference Link telephone
Pros:
Ease of use.
Familiar technology: your basic telephone
Regular phone lines: easy to find people you can talk to.
Portability, drop it in a bag and run!

We have had joint presentations using a conference phone and using a web site for the video/still photos about a project or hike.

Cons:
No face-to-face