Since last year, we at kJube have been regularly using Yugma for desktop sharing and online presentations. It's been working out well as Matt wrote about a year ago.
However, you still need to install Yugma on your machine, and on 64bit (which I've been running since kubuntu 8.04) that has given me some headache.
So I recently had a look at some other tools namely dim dim as well as vyew. Both are fully browser based.
Dim dim started up perfectly both on my kubuntu 9.10 as on my Mac G5. However I soon discovered that screensharing was 'to be released for Mac and Linux in Q2'. And that is a least a month away. Even though the other functionalities of dim dim looked ok, screensharing is really the main thing I was looking for, so I skipped dim dim and moved to vyew.
And I must say that after a short test vyew.com came out as a serious piece of software. I created an account and started a meeting on my Mac in less than 2 minutes, invited myself on my Linux machine and started the software also there. Fully browser based, no installation on either of the machines and working out of the box.
Not only did the screensharing work, also VoIP and camera seemed to work. Wheeew. I must say, this came as an extremely pleasant surprise.
Below you can see a screenshot of me using vyew, sharing some Pentaho Data Integration work with myself during a late evening meeting. We really got a lot done :-)
Anyhow, if you are looking for an free (up to 20 persons in a meeting) online collaboration tool, try vyew! Also it has some cool features for collaborative editing of documents. Only minor remark: screen rendering is sometimes slow. But how fast do you want to run over the screen when on the other side people are expecting you to go slow so they can follow?
When I tried to let Harris share his desktop today, I became painfully aware that desktop sharing from Mac to Linux works nicely. However the other direction doesn't. As the people of Vyew say themselves "pretty lame". Still they are ahead of dim dim, having desktop sharing work on Mac already. Sorry for this post being not completely correct.