Here are some scripts to add playdar buttons to some sites. To use, install greasemoney and playdar then click one of the links below.
MusicBrainz: http://github.com/alastair/playdar-scripts/raw/master/musicbrainz_playdar.user.js
Wikipedia: http://github.com/alastair/playdar-scripts/raw/master/wiki_playdar.user.js