ScreenGrab! is better now with the new version:

It will save what you can see in the window, the entire page, just a selection, a particular frame... basically it saves webpages as images.
Firefox Universal Uploader:

As the name says, this firefox extension allows you to upload/download files from any website using a friendly interface. Upload files/photos/videos to Flickr, Picasa, Youtube and Box.net (1GB of free space) in this version. Next versions would support other websites like Google Videos, Webshots etc. You can add multiple files to the queue at a time. Extension will take care of uploading them for you.
404: Page is Not Found ? Now it will be!:

If a page was (re)moved and now shows '404 page/file/site not found' error, this tiny extension uploads archived version of a page (from wayback machine at archive.org).
GUtil!:

50 Google® Utilities in your Firefox Menu and Toolbar.

GUtil! adds 50 Google® Utilities in your Firefox Menu and Toolbar.
You can choose the services you want, or not.
Page Title Eraser:

The Page Title Eraser (PTE) is a simple Mozilla Firefox extension which allows to hide title and icon (favicon.ico) of the selected tab. It provides more privacy at your workplace.