I've had my hand at a pony-themed track;
http://soundcloud.com/nick-porter/har-d ... gle-at-the
Not too great, but I'm proud of it. Currently working on a few more different ideas in both electronic and flute form.
For other stuff I love;
MictheMicrophone is amazing.
So is TheLivingTombstone.
AlexS+Omnipony are sweet.
Archie V had a cool Becoming Popular mix.
PinkiePieSwear was my inspiration to make pony music, man.
Underpony made an awesome remix of Sunshine and Celery Stalks.