Some download managers, for example freeware Orbit Downloader, support RapidShare and other files sharing services. It won't help you to get as many features as its premium accounts do, but it downloads files better than a web browser.

rapidgrab can help. It uses premium accounts to help you to download files for you. When it works it is very helpful, especially for those who have slow Internet connection since, because premium account allows to use download managers and resumable downloads. (thanx Kron for the tip)