If your Internet connection requires you to use a proxy which needs a username and password, Authoxy may be the solution to a seamless Internet experience. Authoxy runs locally as a proxy server to intercept HTTP and HTTPS requests, forwarding them on to your regular proxy with authentication details you define in a System Preference Pane. Such a process is required to use many web services (MacHelp, QuickTime, iTunes) behind a proxy requiring authentication.
This is an older version of Authoxy for those running Mac OS X 10.1 - 10.1.5
lxAuthoxy is a support program to Authoxy, which runs as a plug-in to Location X. Location X brings back the functionality of the pre-OS X Location Manager, allowing you to define sets of preferences (called locations) which can easily switch between. lxAuthoxy adds the ability to switch Authoxy settings.