Private IP Option

So im interested to know what funky solutions/tricks people are doing with the new private ip feature, apart from your typical H.A/Takeover situation.

Me personally im using it for a mysql/mail server in the sense that i have my mail gateway out for the world to see, do filtering etc, and then it passes it back to my server via the private ip for final delivery.

I was trying to think what other kewl funky things we could set up on it.. Maybe interms of with other linoders for sharing some services etc.