flex lib proect:

Just like the corelib project for the collection of Actionscript3 api's ,the flexlib project has also started on codes.google.com for the collection of the custom flex component.
These components are open source and I think any body can contribute to this library.

But the contributed components has to be a pure Actionscript3 code and not mxml classes.

Library has a beatifull asDoc documentation which explains all the Apis.The downloadable zip of the library also contains the example for each component demonstrating their use.

We just need to include this library in our project and then use it as imported class or the user defined namespce.

ex:
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" xmlns:flexlib="class path to flexlib library" > <flexlib:compoentName > <!-- properties to set --> </flexlib:compoentName >


more information on
http://code.google.com/p/flexlib/