Cross-platform virtual meetings

[Joe]

My company is in the process of trying to set up virtual meetings,
including things like screencasting/sharing, voice, video, whiteboard,
etc. The office is all Mac, our clients are mostly Windows, and I'm on
Linux. We've been trying to find something that will work for everyone
and is easy to use, but so far haven't come up with much. Webex seems to
work, but I can't get screen or document sharing to work from Linux, and
it also lacks voice. Most of the others either didn't run at all or
don't have any Linux client.

Recently I set up a VNC server on my machine and used our VPN to
broadcast back to the office and Skype to handle the audio. It worked,
but not well, and it's definitely not something that we can use with our
clients.

So, fellow Linux users, got any other suggestions for what I should be
using? I'd settle for something that didn't have voice if everything
else worked really well, but of course, I'd like to have everything in
one package.

-Joe