What tools do I need to develop in ActionScript (in Linux)

I have written a blog entry on how to setup Eclipse + AXDT + Flex SDK to prepare your mxml/actionscript (as3) development environment on Linux. If you are interested, you can have a look here: http://netpatia.blogspot.com/2009/09/flash-development-on-linux.html

A Windows or Mac box. :-)

just kidding, actually you can use the Flex 3 SDK mentioned above and compile using the CLI. If these AS3 Libraries are indeed Flex libraries (sometimes there are discrepancies between what works in Flex, what works in CS3, and what works in both) then you should be able to import them and use them.

Also, I've never tried it myself, but Flex Builder is based on Eclipse and I believe there's a way to configure Eclipse to compile with the opensource Flex compile if you'd rather work in a graphical IDE.

I've had very good experiences with Sprouts. It is a ruby wrapper for the Flex SDK that allows building with Rake and easily hooks into continuous integration engines.

http://www.projectsprouts.com/

It looks like the Flex 3 sdk (http://www.adobe.com/products/flex/flexdownloads/index.html) is a good place to start. Any other suggestions?