Buy some older Qualcomm VOIP gear, sells for pennies on the dollar used, update the firmware and install the Video stuff. Call Qualcomm once you've got the gear and register, then you get all the extra stuff they don't advertise.

OR

If you have laptops with linux and it's one on one. Use the empathy video/voice plugin. It's nimble and fast.

OR

Openmeeting, it's kind of interesting and it's free if you want to keep it in the house.
[link to openmeetings.apache.org]

OR

Free online service. I've heard mixed reviews.
[link to ubiqq.com]