There are no really 100% good cheap solutions what I know about but OPT may be a good solution licensed under GNU General Public License (GPL).

OPT is a PHP web-based generic project development virtual common place offering easy access to project information such as tasks, requests, e-mail, trouble tickets, documents plus a couple of other features. Uses LAMP (plus experimental Windows support)
Another (not free) solution which can be of interest is Genesys meeting center.

Meet and work, online
Genesys Meeting Center puts you in control of your virtual meetings, online. You visualize and manage your meetings from your PC. One simple interface integrating audio, web and video conferencing, makes conferencing online as easy as “point” and “click”. Your meeting room is available 24 hours a day, 7 days a week.

A fully interactive virtual conference room
With Genesys Meeting Center, your virtual meetings are instantly more visual and dynamic. You can present PowerPoint® slides, share applications and even be seen by your participants with multi-point desktop video.

Collaborate in real-time
Now you and your participants can approve, edit or amend any type of business documents. Correct or modify legal documents, sales proposals, architectural drafts, CAD drawings, and virtually any other application that you can run on your computer.

Easy to start. Easy to join.
Schedule your meeting online, from your Microsoft Outlook® interface. Or quick start a presentation right away from the Genesys Meeting Center home page, or via your MSN® Messenger. Participants may log-in to your meeting through or through a direct link sent out via e-mail. Those without Internet access may still access and follow the audio call via telephone.
There are ofcourse many other solutions like the above another possible solution could be sametime but this is ofcourse all depending in what the demands are and how much work you want to do yourself and the price ofcourse .