WebEx released a plug-in that enables Yahoo instant messengers to "co-browse" websites at the same time. My wife and I actually used it the other day when she was showing me some XMAS presents she wanted to buy. In the past, she would copy and paste the URL's into IM. I would then have to click on the URL's and navigate on my own until I found the product she described to me over the phone.
With the new WebEx plug-in for Yahoo IM, we browsed the sites together. She navigated and I simply followed along and saw everything she did on the browser.
You can download the plug in here: www.webex.com/go/yahoo