Firefox only (Windows/Mac/Linux): The FEBE Firefox extension backs up all of your existing Firefox extensions with the click of a button. We’ve featured FEBE before, but it’s improved significantly since then, and the latest update has added support for automatically uploading your extension backups to file-sharing web site Box.net. FEBE can schedule automatic backups, and in addition to your extensions, FEBE can also back up and restore themes, bookmarks, preferences, passwords, and virtually anything else in your Firefox profile. In fact, if I didn’t know any better I’d say FEBE is venturing toward full Firefox profile syncing (we can only hope). FEBE is free, works wherever Firefox does.