The Unofficial Yamaha PSR Resource Site has a huge searchable index of MIDI files for your listening pleasure, especially some intended for Yamaha instruments (like my digital piano).
This is BrainLog, a blog by Dan Sanderson. Older entries, from October 1999 through September 2010, are preserved for posterity, but are no longer maintained. See the front page and newer entries.
March 12, 2003