Apps with 'HTTP Monitoring' feature
Fiddler is a Web Debugging Proxy which logs all HTTP(S) traffic between your computer and the Internet.
Reverse proxy and HTTP proxy and monitor that displays all HTTP(S) traffic to/from your computer.
HTTP Debugger Pro - A Professional HTTP Sniffer and Analyzer for Developers
Packetriot makes it simple to expose services and data on local and private networks to the Internet.
Driftnet is a program which listens to network traffic and picks out images from TCP streams it observes.
NodePing Server Monitoring and Web Site Monitoring. Simple but powerful Internet service monitoring. Checks as frequent as once a minute.
Log all traffic on your network card. Analyze and parse network packets. Capture transmitted files and passwords.
Working quietly on the Menubar, Surge is a high-performance HTTP/SOCKS5 proxy server.
EtherPEG is a free program for the Macintosh that shows you all the JPEGs (and GIFs) going by on your network.No screenshots yet
RequestBin.com gives you a URL that collects requests you send to it so you can inspect them in a human-friendly way.
Speedrank monitors the performance of your website in the background. It displays Lighthouse reports over time and delivers recommendations for improvement. Speedrank is a paid product with 14-day-trial.
Suspected of distribute adwares, even after removing the extension
HTTP Headers allows you to quickly see the HTTP header information for the current URL.
NetStat Agent is a powerful and easy-to-use network toolkit for monitoring and diagnosing.
Webmon is a Realtime Website Monitoring and Escalation Service.
The AnyWHERE extension allows you to trivially spoof the responses to browsers' GeoLocation web service queries. It works with IE9, FF4, Chrome and Opera.