Replay Media Catcher Always works and it can do what you're asking i.e, multiple videos at once Highly recommended
Dude, it is an addon for firefox. IDK if it works anymore but I know it used to work on youtube anyway. It actually should still work dude.
I use Internet download manager it places download button above the video and downloads every video very easily
What I am using is the youtube downloader from Sothink, and I am very satisified with the software. There are two editions for the video downloader actually: one is the stand-alone version, which supports many browsers but needs to be paid for the full version, and the other one is the Firefox extension, which only supporrs Firefox but is for free. the domain name of the official website is sothinkmedia, and hope that helps!
Net Video Hunter i am using, it is a add-on for the firefox, and by use of this you can download multiple video at a single time, it is a good application, it can download from all the websites like Youtube, Dailymotion, Metacafe etc.