Benign Internet monitoring tool?

Our corporate HQ has "strongly recommended" that we keep track of Internet sites visited by employees, so I have to implement something. Personally I find it excessively intrusive to log who visited which site. What I would prefer to do is get a list of all the sites visited and then highlight problem ones and feed this back to all employees.

Unfortunately I can't find any software which does just this. Most of it involves keylogging, which I don't require, or monitors individual usage. Is there anything available which does what I envisage?

Or could I route the Internet access through a Windows 2003 server and monitor it via something there?