The problem with using Ethereal for this is that it requires that a capture file be generated for analysis. This can be done but it is rather difficult to automate continuously. The capture log, even with filters can get rather huge. There's also no easy way to deal with redundant requests to the same web pile.
Try Syslog or SNMP traps.
I'll assume that the WRT54G is using non-Linksys firmware. Turn on Syslog in the WRT54G and point it at a Windoze monitoring server. Install some kind of Syslog capture and reporting program.that this program will also do SNMP trap logging. I suggest you just look at what syslog generates and see if there's anything that can be filtered (grep) into a report.
SNMP traps can be set to generate a UDP trap message every time a web page is accessed. The Linksys BEFxxxx series of routers have this feature built in. I use:monitoring which does exactly what you want. Note that you don't need the Norton Firewall monitoring to use the Linksys log monitor feature.
The problem is that the WRT54G is not configured for generating the necessary SNMP traps. I'm sure Linux can be convinced to do so, but don't have the time and interest to figure it out. You might ask for help on the Log Viewer forums.
I also just blundered across this logger:haven't tried it but it supports the WRT54G and looks like it will work. One catch, $50 shareware.