little program will allow you to make a playlist in the .m3u
simply dragging and dropping one or more music files (.mp3 or
extensions) or playlist files (.m3u file extension) onto it, you
(yet!) drag and drop folders, you can then randomize or sort the
playlist and then save it, it will be saved as a plain text file
the .m3u extension, if you don't add .m3u to the file name it
added for you.
Although this prog was written primarily for Rockbox
the file type is used by a number of different music players and
should be pretty universal.