Monitoring log files

How would you recommend monitoring a service
under NT that uses its own log files rather than raising events in the NT
event log. it would be great if I could take a delimeted log file, parse it
and monitor based on, say keywords within the log. That way I could not
only monitor port 80 traffic, but specific applications which happen to be
using port 80 to display to the end user..... Any ideas??

Thanks,

Andrew