Well, it's a good bet that all Fortune 500 companies do e-business. You could also check Yahoo's directory...just browse looking for top x lists for e-commerce.
Companies such as Nielsen and J.D. Power and Associates rank and give awards to products and companies for many things. For example, during the '98 Winter Olympics, did you see that the Dodge Minivan was rated #1 in its class by J.D. Power and Assoc.?
Who the heck is Gen. Failure and why does he want to read my hard drive?
Soon to come: Aspology.com
Wow... No one has mentioned these sites. I am also wondering if I should share them or keep them to myself...
OK Well we're all friends right? You'll share that info with me in the future right?
Ok here goes.
Check out NetB2B and Advertising Age. Now Not exactly a list of who is who and who is most popular but they are listed by the amount of money they are moving around, who does their advertising and who is buying.
For detailed information check out the Ad Age Dataplace. For specific Internet Properties go to Net Results. The figures are a little old but you'll get a good idea.