I want to see a log.
192.168.0.23 www.example.url 13:34 19 april 2011
tcpdump is a command-line utility to see the traffic on any network interface. It is full-featured, but can require some serious reading of the man page.
Wireshark is a full-featured application that will allow you to see all such traffic. It provides a GUI (X-windows based) into which you can specify filters on traffic and collect statistics. See more info and download it at wireshark.org. I find knowledge of Wireshark to be very, very helpful with lots of network tasks.
Debookee will do the job for the following protocols: HTTP, HTTPS, DNS, TCP, DHCP, SIP ...
There's also a scanner included that can show you all the devices on your network.
But the best to me is the interceptor tool that allows you to see the traffic of any device (mobile, tablet, other Mac or PC) on your network, like Cain & Abel for Windows.