Now that Adobe's released the final bits to Flex 3 with Adobe AIR support, my latest article Digitally signing Adobe AIR applications has been posted over on Adobe DevNet.

Read it if you're interested in understanding a bit about the code signing process, including certificate acquisition, and signing from all the tools Adobe supports AIR application creation from: Flash CS3, Dreamweaver CS3, Flex 3 SDK, and Flex Builder 3.

Cheers.