http://www.cyberciti.biz/faq/custom-nginx-maintenance-page-with-http503/
Article explaining how to create a custom 503 maintenance page and have it served by default in various situations (migrations for example). Very useful.
http://serverfault.com/questions/330638/forward-my-http-requests-from-my-ip-to-another-server
Forwarding all web traffic from an old to a new server with nginx, includes a sample config for nginx. Useful.
http://www.fiddler2.com/fiddler2/
Similar to Charles Proxy, but only on Windows, a web debugger that acts as a proxy between browser and web and allows the user to monitor / modify request on the fly.
http://www.charlesproxy.com/
A paid ($50/user) program that acts as a proxy between browser and web and allows the developer to monitor / modify / etc traffic including SSL. Handy. Want open source.
http://how2i.com/1493/how-to-use-amazon-android-app-store-outside-us
Tips on how to use the Amazon Android google market alternative outside the US. It centres around proxying the IP into the US. Might be possible to tether to a proxied connection, could be simpler.
http://www.glype.com/
A web based proxy script powered by PHP and curl, not free, released under a proprietary license, removing the "powered by glype" link costs money. Free as in beer.