infosys uses gotomeeting for training, really rubbish, I got 6 notebooks in a meeting room 3 can't start up. The FAQ is useless, never solved my issues.
webex, used for several years. Excellent, I never got any problem at all. Client is light weight, and high compatibility.
Microsoft livemeeting, it's annual subscription by the company, seems really cheap. downside is, you need to do client installation.