OSS Video Conference solution?

[Ken D'Ambrosio]

Hey, guys.  I've been tasked with bringing a video conferencing solution
in-house, by strong preference Open Source (for both philosophical as well as
financial reasons).  I've found a couple of promising candidates (e.g., check
out Openmeetings, over at Apache Incubator), but they seem to lack some subtle
things (admin manual, solid user manual, the Flash client seems to crash, the
interface is counterintuitive...).  I'd love to leverage Asterisk, which, since
10.x, has the underpinnings for videoconferencing, but I don't see anything
(OSS) that takes advantage of it.  I'm completely open-minded as to an OSS
solution so long as:

- It's not overly hard to use
- It allows video from multiple sources
- Its client runs on Mac and Windows (Linux is good, but not a deal breaker)
- A minimum of documentation would be wonderful

Any suggestions?