Google has just released an AS3 version of their maps.
it works with Flash and Flex.You just need to import the SWC and write some code to get it working.
get the SWC here
New version of flash player including features like 3d Support, advaced text renderer, Hydra’s effects loader (now Pixel Blender) and the posibility to write local files without using the server.
updated: secocular has written this excellent article!