Pylons is a lightweight web framework emphasizing flexibility and rapid development.
CakePHP is a rapid development framework for PHP that provides an extensible architecture for developing, maintaining, and deploying applications.
Django is a high-level Python Web framework that encourages rapid development and clean, pragmatic design.
Ruby on Rails is an open-source web framework that's optimized for programmer happiness and sustainable productivity. It lets you write beautiful code by favoring convention over configuration.