Charles
Charles is an HTTP proxy / HTTP monitor / Reverse Proxy that enables a developer to view all of the HTTP and SSL / HTTPS traffic between their machine and the Internet. This includes requests, responses and the HTTP headers (which contain the cookies and caching information).
Mono Fiddler
The Linux version of Fiddler.
Need a Linux or Mac build?
Check Out the Alpha Build
For Mono framework
For more details please check Mono Fiddler