If you want create a play list form youtube videos, tubesort is a free apps that will help you to create play list from youtube videos. You can login tubesort via your facebook account.
To add play list simple search videos in youtube via tubesort then the search result will appear bottom of each video result you can see Add to Library button you can simply click on that the video will add on your play list.
You can create different type of play lists. When you play a song the video will also play in tubesort. You can invite other friends to joint tubesort. Tubesort provides lots of options for watching videos i.e. repeat, shuffle etc. You can also change different type of themes for your play list.