Fiddler

Fiddler screenshots

Fiddler is a web debugging proxy that displays Internet traffic from your PC
Main window
Fiddler 2.3 beta : Main window

Alternative downloads

CooCox MDK Plugin
It is a free plugin which allows you to easily debug your project.
1.4.2.1
FREE
IDA
IDA
Disassembles and debugs multiple targets and handles remote applications.
9.3.1
FREE
WCAT Extension for Fiddler
WCAT is the best tool to hammer your web server with requests.
1.0
FREE