Derpibooru is an image booru (sharing/commenting/voting system) specifically aimed at fans of the show My Little Pony: Friendship is Magic. If you haven't watched it, don't knock it till you've tried it.
We wrote the software for Derpibooru from scratch with a view to making a really good web application for sharing images. We hope you like it, and welcome any feedback you may have.
It's not meant to replace or supplant any other boorus for the MLP:FiM fandom, but merely to provide another - hopefully useful - avenue of sharing for the fandom. Because sharing is magic.