Log Parser is a great tool to sift through IIS web logs (or most any other structured data) for information.

Log Parser is freely downloadable online from www.microsoft.com/download (search for "IIS 6.0 Resource Kit Tools" for Log Parser 2.1, and search for "Log Parser" for Log Parser 2.0).

There is a webcast tomorrow, March 17th, 2004 at 11:30 PST about LogParser.  Register at:

http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032243724&Culture=en-US