Me.dium is truly breakthrough. I have been using it since I first saw it at DEMO 07, on the FireFox browser. Now they are through the third beta on the Microsoft Internet Explorer and it is getting pretty stable and even more fun to use.
Go to Me.dium.com and sign-up for an account, it's free. Once you get an account, you can add friends, for example, if you want to add me, my Me.dium user name is MSFTdave. Of course I have a chance to accept you, so if I have no idea who you are, well, I can get rid of you. You can also look folks up by their e-mail and invite them as friends.
See what your friends are up to… Once you have established your friends network, and they have Me.dium installed you can see what web sites they are on in the little friends tab. The friends tab is in the Me.dium side bar that is installed when you install Me.dium. If you want to chat with them about a particular site, you can click chat, or you can just click the site referenced and see what they were looking at. The other day, I noticed one of my friends shopping at Thomas Pink shirts, and since I was in the market for shirts too, I clicked to check it out. I have always been a Brooks Brothers guy, but those Pink shirts look pretty nice.
Every month, as part of my work here at the Emerging Business Team, I look at every business application company that gets funding and is reported through VentureSource. Since we just brought in feeds from Europe as well, I had a big pile this month, 50 companies. Now, my standard practice is to open-up Me.dium as I browse through to each company. You can see where people are coming from (what they browsed prior to visiting) and where they went after – notice how the SAP site showed up here, SAP had just published new benchmarks – which I noticed and went on to investigate. Me.dium goes beyond tracking what your friends are up to. When you install Me.dium, it installs an add-in that keeps track of what you are doing in the browser and reports it back to Me.dium. Ok, yes, there is some trust involved here. It also turns off automatically when you go to your banking site or any secured site. But, based on the tracking of all the Me.dium user behaviors, they do some very, very cool stuff. Me.dium creates this radar view of where you are, where your friends are, and where the world is. The world is filtered down to users that show browser behavior similar to yours – which scopes the radar view down to a few web sites.

Navigation tracking and attention at a whole new level: Because Me.dium is entertaining and useful enough to have a very large audience actively use their application; they are able to gather a tremendous amount of detail on user behavior. Thus individual preferences and navigation trends are available for add placement and market research as well.
Well funded and rapidly adding users, near 20,000 downloads, Me.dium recently raised $15M, led by Waltham, MA, based Commonwealth Venture Capital and joined by Colorado based Appian Ventures and Boston based Spark Capital. That brings their total backing to $20.275 M based on VentureOne.
Me.dium.com