I’ve long been a Fiddler fan. It’s been a super valuable tool for debugging SOAP and REST based code.

http://www.fiddlertool.com/

It rocks, but I often need to debug on the Mac, especially now when doing network programming in Silverlight.

So I recently found WireShark.

It’s free, runs on Windows and Mac, is Open Source, and there are 3rd party builds for other operating systems.

http://www.wireshark.org/