I suppose in short, the answer to your question is no. :)
I wrote a vb program to parse the logs, extracting lines based on input criteria, like ip and username.
I'm not sure what you mean by "which websites were really requested by my users", since the logs show which IP and user is requesting the first URL in the log.
10/10/06 08:55:35 10.0.0.1 sondra 0000029345 Requested:
http://www.google.com/maps?
10/10/06 08:55:36 10.0.0.1 sondra 0000029388 Requested:
http://mt3.google.com/mt?
10/10/06 08:55:36 10.0.0.1 sondra 0000029383 Requested:
http://mt3.google.com/mt?
10/10/06 08:55:36 10.0.0.1 sondra 0000029389 Requested:
http://mt0.google.com/mt?
10/10/06 08:55:36 10.0.0.1 sondra 0000029387 Requested:
http://mt3.google.com/mt?
10/10/06 08:55:36 10.0.0.1 sondra 0000029386 Requested:
http://mt0.google.com/mt?
Obviously I can tell what server Sondra orginally started going to by the first url.
Do you not have usernames setup, or does your log just show 'guest'.