Using Spotify Linux Preview, I want to open URIs to songs and playlist from Opera. This was not working, so here is how you fix it:

Stick the following in a file:

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#!/bin/sh
spotify -u $@

Make it executable with chmod +x

Go to Opera preferences by pressing Alt+P or Ctrl+F12, then go to Advanced, Programs, press Add, in Protocol, enter spotify and put the path to the script in Open with other application. Now you can open all the playlists!