Samrat Man Singh for his amazing tool called VideoDropper.
VideoDropper Lets You Send YouTube Videos Directly To Your DropBox Folder
VideoDropper is a YouTube-to-DropBox web service that simplifies the grabbing of YouTube videos on the fly. VideoDropper allows you download YouTube videos directly to your Dropbox folder, so that you can watch them later at your leisure.
Just login with your Dropbox account, specify the YouTube video URL, and let VideoDropper "drops" that video straight to your DropBox folder.