Ask HN: Web App Deployment Best Practices

I am brand new to web development, but I am around about 70% complete with an application. I think it's about time to start learning how to properly deploy it, but I'm not sure where to start.

I have been looking at EC2, S3, Heroku, Rackspace and some others, but can't piece together what I'd need.

Let's say, for the sake of learning, this app has 50,000 daily users - where could I go to learn a gameplan for such a deployment?

The app I'm building is PHP, but I am interested in what others do for Ruby, Python, Asp etc.