Recommendations - screen sharing application that works on both Mac and Windows??

Hi,

I'm looking for a good application to use in my small business for screen sharing and conference meetings. I use the feature that Skype have brought out extensively, but there are times that I need to share my desktop with multiple viewers and often in environments where Skype is prohibited.
I have found several free applications out there that look promising, I just thought I would ask advice on here first to see if anyone here knows this software and if there are any recommendations - both free and paid software.
Here is a list of the applications which I have found:
Dimdim
Mikogo
Yuuguu
Teamviewer

I would really appreciate any input,

Nigel