well if you have access to the wep/wpa key (assuming a simple network using a PSK and not 802.1x for authentication) you can either associate and sniff the traffic using tools like wireshark or kismet. You mentioned having a copy of BackTrack lying about. Both tools are on it. Then parse the .dump/pcap files for strings that contain urls. Or sniff the traffic using kismet, open the .dump file in wireshark and enter in the WEP/WPA key. http://wiki.wireshark.org/HowToDecrypt802.11 The same can be done using kismet but if you've never used it before then wireshark is probably quickest.

To clear out extraneous data when capturing using wireshark set you capture filter to only capture tcp port 80 & 443 like so: tcp port 80 and tcp port 443

Another option, if you have the capability at your location is to span the switch that your firewall/router is connected to. Then just use wireshark/tcpdump, etc to capture traffic.

HTH,
Dean