There have been a few posts pointing out the fact that the Pogoplug web interface doesn't have any way of creating custom music playlists.  As far as I know it will not recognize the .M3U playlist file extension, but it does let you sort your music files by Songs, Artists, Albums, or Genre.  I've found that you can make a mock playlist by creating a 'Slideshow' with no photos or just one photo and then adding the music to the slide show in the order you'd like to listen to the songs in.  You can name the slideshow the name of the playlist you want and place one .JPG image file if you want it to display anything while playing the music.  Once the music is in the slide show, just click on 'View Slideshow' and wait a few seconds for the first song to play...  They will play in the order you added them to your slideshow.  Of course you could do this by dropping the files in a separate folder and then accessing the drive directly, but this saves time and file duplication.  Unfortunately I have not found a way to shuffle the playlist or have the web interface automatically create playlist for you like some other applications like iTunes do.  At least this is a simple way to put together a playlist that can be accessed any time by title in the Slideshows link under  'My Library'.