Are you looking to quickly make and host a small web app cheaply? Here's the software stack that I use nowadays.
- Python + Django 1.4 (https://www.djangoproject.com/)
- Hosted on Heroku (http://www.heroku.com/)
- A MySql database hosted on Amazon RDS (This is only cost-effective if you have more than 2 sites using the same DB, otherwise, use Heroku's DB)
- Amazon S3 for static file serving
- Twitter Bootstrap for a base CSS/JS stack
- Stripe.com for payments
- Desk.com for help desk
- BitBucket.org for source control (GitHub for open source stuff)
- Pusher.com if I need real-time / push capabilities
Using that stack I can get a new (small) site up and running for almost no incremental cost.