I threw together a Spotify API program called song-basket. I have a few large themed playlists (for example, Instrumental Funk). This app is to help me add songs to them. I can choose a playlist (the basket), and then as I surf around Spotify, it lets me add the current song to the basket with one click. It also shows me whether the current song is already in the basket or not, which they often are. If the song is already in the basket, I don’t have to think about whether to add it, and I don’t have to deal with the annoying “Add duplicate?” question.
This started as an example in the Tekore docs, and I hacked at it until it did what I wanted. A lot of it is wrong: no templating, incorrect HTML, a stateful web application, horrid styling, and so on. It doesn’t matter, it’s a quick app to do what I need. If I want, I can polish it later.