Inbound emails are with the help of the lovely guys at PostMark - http://postmarkapp.com. They have webhooks. That'll post inbound emails as JSON to your app.
Other than that, Rails + Postgresql + Nginx + Redis
Wow I hadn't heard of postmark. That would make processing emails from users really easy!
Now I just need to think of a business idea where I process emails from users. Hmm, how about a service where users can forward emails and it automatically creates an appointment on their calendar?
Other than that, Rails + Postgresql + Nginx + Redis