For RapidShare: https://addons.mozilla.org/en-US/firefox/addon/66584/
For MegaUpload: https://addons.mozilla.org/en-US/firefox/addon/15051/

Mkay, so I was browsing and I found these two add-ons that make downloading stuff from RS and MU slightly better. It monitors the waiting time, and when the waiting time has finished, it'll automatically start your download. It's nice cause you don't have to pay attention to it, and if you go to another tab and wind up forgetting about it, like I do, then the session won't expire and you won't have to go through the steps again.