MusicBee to Google Music playlist sync
Note: This has stopped working because Google have deprecated the Client Login API. When I have time I'll see if I can get it working another way.
My favourite music player for Windows is MusicBee. It's fast with large libraries, is full of useful features and utilities and is easily expandable with plugins. I wrote a utility to synchronise playlists from MusicBee to Google Music, allowing me to use those playlists on my phone.
Rather than upload the music itself, the utility assumed that the libraries were already in sync. It created each playlist in the target library and then added each song in turn to it. The source is on GitHub and there's more on the MusicBee wiki.