With regards to playlisting my digital music collection in novel and interesting ways, I've found Plexamp's "Guest DJ" feature [1] to be second to none.

It's not the cheapest piece of software. However when viewed in comparison to the cost of a standalone mp3-player, I think Plex's $119.99 Lifetime Pass is justifiable.

[1] https://mobile.twitter.com/plexamp/status/158570440123829863...