Force.com Adobe Flash Builder is a  jointly developed integrated development environment (IDE) that gives developers a single, powerful tool for building cloud-based rich Internet applications (RIAs).

:: View the recorded webinar on Force.com Adobe Flash Builder
http://wiki.developerforce.com/index.php/Tech_Talk:_Adobe_Flash_Builder_for_Force.com

:: Reference other resources
http://developer.force.com/flashbuilder
http://www.adobe.com/devnet/salesforce/index.html