web2py is a free, open-source web framework for agile development of secure database-driven web applications; it is written in Python.

web2py is a full-stack framework. It includes an ORM (called the Data Abstraction Layer), its own template engine and typical form widget helpers and controls.

Created by a team of professionals and academics, one of its key principles is no backward incompatible changes. Development is led by Massimo Di Pierro, Associate Professor in Computer Science at DePaul University in Chicago.

Additional resources:

1. Project Website
2. Documentation
3. Source Code
4. Sample Websites
5. Wikipedia Page
6. Google Group

Simple Example (from What is web2py?):

Model Definition:

db=DAL('sqlite://storage.db')
db.define_table('image', 
    Field('name'),
    Field('file','upload'))

Controller:

def index():
    form = SQLFORM(db.image)
    if form.process().accepted:
        response.flash = 'image uploaded'
    return dict(form = form,counter=None,_class='boxCode')

View:

{{extend 'layout.html'}}
<h1>Image upload form</h1>
{{form}}