this is my very first question on SO, so I'll do my best.
Every one know a really cool thing for looking through website's traffic under Windows – HttpWatch. It is really useful program for developer and I'm missing since I've changed my OS from Windows to OS X. So my question is "Are there some kind of alternative for this program (I don't mind if it is just extension for browser, or native app, or cmd line tool) under OS X and Linux/BSD?".
If you just want to look at the web browsers traffic, you can use the Network tab of the Deveoper tab, which you can find on Chrome by pressing F12. If you prefer Firefox, you can try using Firebug as well.
But if you want to see the traffic of all applications, not just the web browser, I suggest you take a look at Wireshark.