1. Minimal Comps
Minimal Comps are a set of Flash-based User Interface Components written in ActionScript 3.0 by Keith Peters of www.BIT-101.com.
The key point is that these components are lightweight and extremely easy to use. They are ideal for experimenting and prototyping. They do not have all the features that you would find in, say, Flex. And they probably aren’t what you want for a complex, data-driven enterprise site with a complex layout. But then again, they are a tiny, tiny fraction of the size, and have a tiny fraction of the learning curve of Flex components.