SubWeb is a proxy/reverse proxy for HTTP flows. It is possible
with SubWeb to handle and visualize HTTP request, headers, body
on the fly.

It has three operating modes : proxy, reverse proxy, and midproxy
(a proxy which requires the pages from another proxy). It can
also act as a virtual web server, i.e. answer certain request
based on keyword match.

SubWeb can also allow filtering, and is highly customizable.

WWW:  http://www.hsc-labs.com/tools/subweb/