Need to monitor HTTP traffic

[Hal Vaughan <hal@thresholddigital.com>]

I've been working on a problem for several days, and need to create a 
shortcut.  I've found a program called Ettercap, which lets me monitor 
network connections, but I can't find a way to monitor HTTP connections from 
my browser to a web site, which is what I really need to do.  (Unless I 
missed something, which is possible after several days with almost no 
sleep...)

Is there a program that I can run on my system that can monitor traffic on a 
port, including listing it?  I need to see the headers on HTTP requests and 
responses to see what goes between my browser and the web site.

I don't mean just telling me that packets are going out, or what their 
destination is.  I also need to see the content of the packages.

What can I use to do this?

Any help or alternatives is appreciated!

Hal