Best web conferencing alternative to WebEx, MS office live - Dimdim

Now a days it is common to see huge advantage of having web conference facilities to foster and eliminate geographically distributed nature of work environment. It is also handy for presenting anything without physically present in particular location.
I am exploring best web conferencing alternative to WebEx, MS office live. Here is my findings
1. WebEx - has been there in market for long and I used it from 2003 for official purpose
2. Microsoft Office Live meeting - It is good and intended to knock off WebEx and other similar product as they have near monopoly among big enterprises.
They charges huge money for these services and I am exploring free alternative, if any.
Also the tool should be compatible with multiple platform like MS PC, Apple, Linux (opensolaris) etc.
There is a good read about multiple product here http://www.masternewmedia.org/2003/11/13/best_web_and_videoconferencing_alternatives.htm

Another type of Tool which enable access to remote desktop through internet will be very handy not only to help fix the issue remotely. There are tools to do that
1. WebEx's PCNow - 30 days trail available
2. GoToMyPC - -again 30 days free
3. LogMeIn

Open Source Collaboration Tool

I also found dimdim, it is open source. It is good that product like dimdim comes into market and make others to reduce the price or make the money realize its meaningful value. After using dimdim, i felt really good. We can share desktop, can multiple people dial-in to conference etc. It is more than sufficient to most of my activities. Good work Dimdim. You are instrumental in changing this space.