There is an easy way to return to videos that you view on YouTube later but it requires a Google account. Simply add the videos to a playlist and access them on YouTube whenever you are signed into your Google account. If you use Gmail you already have the necessary Google account.
YouTube playlists are great for creating collections of similar videos. You can separate videos by genre, type or any category that you choose. When you want to look at these videos later you simply refer to your playlist. The playlist allows you to play videos in sequence or shuffled and the playlist can be automatically repeated after all videos are played.