I’m sure this is not the first place for you to hear this but Adobe AIR (Adobe Integrated Runtime) is now shipping!
It’s cool with AIR to be able to build your own desktop apps that just are useful (instead of having a grand commercial purpose); I know I regularly find features I’d like to see in existing apps. Knowing Actionscript 3 and reading a little documentation is all that is needed to build and app that does a better job yourself;)
I see myself doing a lot more AIR stuff in the near future. The performance is still far away from a regular desktop app built on system level languages but instead we get the simplicity of Actionscript to do powerful stuff. With Actionscript also of course working online we can build online and offline applications that save the same codebase. Sweet stuff!