Introducing fireFTP, a cross-platform FTP client for Mozilla Firefox which provides easy and intuitive access to FTP servers. NOTE: This program is still in 'beta' meaning that while it works just fine, it is still in development and there are still features and improvements to be made.
User Agent Switcher Extension on chrispederick.com adds a menu to switch the user agent of the browser. It is designed to provide functionality similar to the "Browser Identification" feature of Opera and allows you to configure the list of user agents to display in the menu.
One of these completely hosed my Firefox install so badly, I had to uninstall and reinstall Firefox just to get it to start up in "safe mode". For now, I've got User Agent Switcher working. But fireFTP remains in the penalty box.