mixmello is a free, open source tool to create remixed versions of your favourite playlists. Search for the Spotify playlist you want to remix, tailor the remixes to your liking (with song previews), then save the playlist with a single click.
I love this thing! I wish it would work for my larger (500-600 song) playlists though. It seems to max out before 100. After that, it doesn't parse the whole list when adding to spotify. I would even pay for this if it was able to do that. Truly, awesome little program!