Well, we launched Postach.io officially yesterday and a ton of people signed up, mostly thanks to some great coverage on Hacker News. We thought we'd feature a few of the sites that launched and were customized.
Isomorphis
http://isomorphis.postach.io/

QuoteRobot
http://blog.quoterobot.com

Hello Stanley
http://hellostanley.postach.io/

Bootstrapping in the Boston Metro
http://forrestblount.postach.io/

On Thoughts
http://onthoughts.postach.io/

If you've customized your Postach.io, let us know and we'll feature you in a blog post :) Comments and suggestions are welcome below!