A beta version of the declarative graphics language Degrafa was released recently to google code. Degrafa is cool because it provides an easy way to do things that are normally unnecessarily complicated in Flex like linear gradients, gradients around rounded strokes, repeating shapes, etc.
Degrafa doesn't allow you to do anything new in Flex - it just makes the things you already do easier. It adds some more complex building blocks to your current set, making programmatic graphics and skinning a far less painful task.
Degrafa is also a good example of a real working open source Flex project. A small team of really talented developers (including my co-worker Andy) from many different organizations got together and made this work in a really short time. A lot of the rest of us dream great dreams and gather small groups of like minded developers, but inevitably client work gets in the way of open source development and our projects fall by the wayside -- this didn't. Check it out.