Now I like this. Delexa.org combines, wait for it, Del.icio.us and Alexa to create a tool that finds the most trafficked Web sites by topic tags. Search for a topic and Delexa brings up a list of Web sites along with their Alexa Rank and the number of Del.icio.us tags the site has. These are combined to give each site a "Delexa Rank."
I like this combined method for determining rank and I like the clean URL you get. For instance my search for "emailmarketing" has the URL http://www.delexa.org/tag/emailmarketing. Maybe I'll tag that on Del.icio.us and create an infinite loop.
You can also search by Web site and Delexa will bring up an Alexa-like information page about it along with all it's Del.icio.us tags and related sites. This is less useful, but still pretty cool.
It's not perfect, it claimed a few sites had no Del.icio.us tags when I know they do and, of course, it relies on the flawed nature of Alexa's user base to determine popularity. Plus it's not very pretty, but I'm sure it will get a face-lift if it stays around. But I'm still calling this worth checking out.