FEBE (Firefox Environment Backup Extension) allows you to quickly and easily backup your Firefox extensions. In fact, it goes beyond just backing up -- It will actually rebuild your extensions individually into installable .xpi files. Now you can easily synchronize your office and home browsers.
Not perfect, but the best multiple-session-in-one-browser solution I know of: "CookieSwap is a Firefox/Mozilla extension that enables you to maintain numerous sets or "profiles" of cookies that you can quickly swap between while browsing."
This project offers extensions of Spring-Framework and Spring-Modules components, either making existing functionality easier and configurable or providing additional functionalities within the same context. This project complements these two frameworks.
Have you ever been interested in what extensions are available for Firebug? If yes, take a look at what I have found. Frankly, I was quite surprised how many Firebug extensions already exists out there.