If you want an online music player, Vattoz is music Search Engine. It searches for songs based on artist name or the song name and displays the results here you can see two options play the song or add to play list. After creation of your play list you can also share your play list with friends.
The play list is a box which could be dragged and dropped anywhere on the web page. Your play list does not lose until you clear browser’s cache.
Check jampri.com out. It lets you do the same but friends have edit access to your playlist and can offer new songs. Pretty nit for creating playlist for wedding or any event.