Download from Rapidshare with RDown Rapidshare Downloader, an add-on for firefox.It provides an automated mechanism to download all your rapidshare files, overnight.
Rapidshare continues to be the world’s largest and widely used file hosting service on the web. Whenever you have large files to download from rapidshare, you would prefer a download manager that can manage all rapidshare links to automatically download the files.This is exactly what this firefox add-on does.
It is a simple add-on that works in the background.All you need to do to download files from rapidshare is to simply install this add-on. Once installed, there will be a small icon on the bottom right corner of the Firefox browser interface. Double click this icon to open “RDown Rapidshare Downloader” and paste as many links as you want. The add-on will take care of automatically processing them, one by one. You can leave it to complete the download overnight or in the background when you are busy working on something else.

Free download the firefox add-on from here.
Update: This add-on is no longer available.
You can also check out the ultimate JDownloader for megaupload rapidshare downloads and skipscreen for rapidshare free downloads via the firefox browser.