Adobe’s Flex and Apollo (still in “Adobe Labs” stage) both use Flash technology. Both are worth checking out.
About Flex:
Adobe® Flexâ„¢ 2 software is a rich Internet application framework based on Adobe Flash® that will enable you to productively create beautiful, scalable applications that can reach virtually anyone on any platform. It includes a powerful, Eclipseâ„¢ based development tool, an extensive visual component library, and high-performance data services enabling you to meet your applications’ most demanding needs.
About Apollo:
Apollo is a cross-OS runtime that allows developers to leverage their existing web development skills (Flash, Flex, HTML, Ajax) to build and deploy desktop RIA’s.