I have an older no-name mp3 player, which I would like to use with iTunes. This can be accomplished with the help of a small free software called iTunes agent.

To make it work, I just had to make a play-list in iTunes, and afterwards setup iTunes agent to synchronize this playlist with my mp3 player. In order for iTunes agent to recognize the player, I had to give iTunes agent the name of a folder on the player.

Just note that this software only synchronizes the player with the iTunes play-list, it does not convert any files, and many mp3 players are unable to play the iTunes default format.