The cliget add-on allows you to download files using curl or wget. This add-on generates curl/wget commands that emulate the request as though it’s coming from your browser allowing you to download protected files directly to a separate machine (e.g. server).
Here is a little more information about cliget from the developers:
Download protected files using curl or wget. This addon will generate curl/wget commands that emulate the request as though it’s coming from your browser by sending the same cookies, user agent string and referrer. With this addon you can download email attachments, purcahsed software/media, source code from a private repository to a remote server without having to download the files locally first. This addon should work with any website; if you find a website that cliget doesn’t work well with, please let me know.
Want to pick up this add-on? You can get cliget from the Firefox Add-ons website.