Some things that I have tried that work cross platform, mostly because 
they run in a browser:

ustream - http://www.ustream.tv - works well for one-to-many broadcasting
mebeam - http://www.mebeam.com - multipoint conferencing
stickam - http://www.stickam.com - multipoint conferencing


Ed wrote:
> On Mon, Mar 23, 2009 at 11:58 AM, Joe <lists@joefleming.net> wrote:
>   
>> Thanks for that, I had no idea Adobe had anything like this. The only
>> downfall is it's limited to 15 participants at a time. Their Connect Pro
>> solution might work though, I don't see anything about a participant
>> limit. They don't have pricing for that online though, which leads me to
>> believe it's pretty expensive. Still, thanks, we'll check that out!
>>
>> -Joe
>>
>>     
>
> Joe -
> If you get more than a few folks into a meeting you want broadcast not
> conference ware - icecast will broadcast audio & video, good for a
> group that doesnt need to interact in channel. Pair icecast with an
> Asterisk VoIP conference for audio feeedback and you should be able to
> handle a good size group.
> Ed
>
>   
>> Judd Pickell wrote:
>>     
>>> This works on macs, windows and linux:
>>> http://www.adobe.com/products/acrobatconnect/ but not entirely sure if it is
>>> everything you are looking for. There is also a pro version which may offer
>>> more features that would be useful.
>>>
>>>
>>> On Mon, Mar 23, 2009 at 11:06 AM, Joe <lists@joefleming.net> wrote:
>>>
>>>       
>>>> 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
>>>>