A working link is http://www.usa.att.com/callvantage/index.jsp?soac=76993. That’s snappy. Of course, you can navigate down from www.att.com to find the service as well.
[note: After I logged the post below, the url started working as you would expect it to and took users directly to the CallVantage pages on AT&T's website. Several commenters pointed that out. Not sure why it wasn't working in the morning or what got it working again.]
I was looking for a link to AT&T’s VoIP Service, AT&T CallVantage and tried www.callvantage.com. Hard to believe that AT&T marketing (and its competitors) are so fast asleep that I got the result below. Maybe it means that the days of cyber-squatting are over.