The following list contains the most important Firefox download extensions. The concentration on the most important (and not an overinflated list) makes it easier for anyone to handpick the best download extensions from the list.

The list is divided into the categories files, images, movies and misc. Each category lists a handful of extensions linking directly to their download page at the Mozilla website.

Files

Down Them All – Firefox Download Manager.

Fire FTP – ftp client for the Firefox web browser.

Flash Got – Download Manager integration in Firefox.

Get Filesize – Retrieves the file size of a selected file.

Save File To – Makes it possible to save files into custom folders without having to open the file browser.

Spiderzilla – A website mirroring software based on the excellent HTTrack.

Images

Image Grabber – Download images that are protected by a transparent spacer image.

Save Image In Folder – Save images in personalized folders.

Save Images – Saves the images from the current tab to a specified location.

Movies

MP4 Youtube Downloader – Downloads Youtube videos as mp4 videos.

Flash Video Resource Downloader – Compatible to most flash video websites.

Video Download Helper – Excellent video downloader that is compatible with hundreds of video portals on the Internet.

Misc

Amazon S3 Firefox Organizer – Helps you organize/manage/store your files on Amazon S3

Clean And Close – Replaces the clean up button in the Firefox Download Manager with a clean and close button.

Download Rapidshare @ Office – The add-on converts all Rapidshare download urls to IP and uses the IP to download them.

Download Sort – The extension saves downloads automatically into different folders.

Download Status – Displays detailed download information like the average download speed, the time remaining and the number of files.

Download Statusbar – Displays downloads in a status bar instead of the default download manager window.

Link Alert – Changes the mouse cursor according to the file type.

MD5 Hasher – Calculates hashes of files that have been downloaded to the local computer.

Open Download – Allows to download and open any file from the Internet in the default application for that file type.

RDown – Rapidshare Downloader – Rapidshare Download helper.

Snap Links – Use the right mouse button to mark multiple links at once.

Did we miss any noteworthy extension? Let us know in the comments.