Compass is a stylesheet authoring framework that makes your stylesheets and markup easier to build and maintain. With compass, you write your stylesheets in Sass instead of CSS. Using the power of Sass Mixins and the Compass community, you can apply battle-tested styles from frameworks like Blueprint to your stylesheets instead of your markup.

flixel is a completely free collection of Actionscript 3 files that helps organize, automate, and optimize Flash games; an object-oriented framework that lets anyone create original and complex games with thousands of objects on screen in just a few hours.

Opensource iPhone simulator for Mac OsX

A mini-framework for Django for creating RESTful APIs.

Piston is a relatively small Django application that lets you
create application programming interfaces (API) for your sites.

It has several unique features:
Ties into Django's internal mechanisms.
Supports OAuth out of the box (as well as Basic/Digest or custom auth.)
Doesn't require tying to models, allowing arbitrary resources.
Speaks JSON, YAML, Python Pickle & XML (and HATEOAS.)
Ships with a convenient reusable library in Python
Respects and encourages proper use of HTTP (status codes, …)
Has built in (optional) form validation (via Django), throttling, etc.
Supports streaming, with a small memory footprint.
Stays out of your way.