Being able to download Youtube videos is not exactly what was intended by the owners of Youtube. However, it seems as though they have turned a somewhat blind eye to the practice. This is why applications like minitube keep getting developed.
Minutube, a simple application which you can use to download and play YouTube videos without Flash, has reached version 1.7.
Among the most important changes in Minitube 1.7 are:
Clickable usernames in the playlist (so you can see more videos from a certain user/channel)
“Manually start playing” option
“Stop after this video” option
Window “Float on Top” option
Ability to skip to the previous video