The following statistics are from the latest Verisign Domain Industry Brief.
Renewals
Renewal rates for .com and .net averaged 76 percent for the second quarter of 2006.
The renewal rate of domain names previously renewed was 85 percent compared to
a renewal rate of 65 percent for domain names going through their first renewal cycle.
The renewal rate improvement comes from increasing renewal rates for previously
renewed domain names.

Active Websites

26% of .COM and .NET domains are parked, 60% have live web sites and 14% do not have a website.

[via Verisign Domain Industry Brief]