There have been many ups and downs when it comes to pulling the videos that you want back off the web and with youtube constantly updating their streaming protocols certain browser extensions such as BYTubeD no longer work. It is for that reason that I am going to list the ones that still work.
Update: Check out the latest post on this subject here:
old_UPDATED: As of DECEMBER 2013 This method of downloading will no longer work due to Youtube’s modification of how videos are streamed. I have created and updated thread HERE with the most up to date method of downloading. The rest of this post will remain for those who are investigating multiple techniques. Thanks ProjectileObjects
Ripping Videos from Youtube for VJing Batch downloading and converting on your MAC
Click here to view the rest of the post!