We released an alpha version of Adobe AIR for Linux today so now we've got some form of support for Mac, Windows, and Linux with the exact same code/.air file. I've been playing with it for a few weeks and it's really impressive to see most AIR applications just work on Linux exactly the way they do on Mac or Windows. Linux support is one of the things I'm most excited about with AIR because I love using Ubuntu and I hope that a lot of the applications I use will be built on AIR so I can spend more time in Linux and have the same experience I do on Mac/Win.
We also announced we're joining the Linux Foundation so we can help push the idea of RIAs on Linux. In addition to the AIR Linux release we also released an updated alpha version of Flex Builder for Linux so we're hoping developers can both build AND consume RIAs on Linux.
We're working on a 1.1 version of AIR that will include some localization as well as some bug fixes from the 1.0 release. The Linux 1.1 version will lag a little but but after 1.0 our plan is to release a Linux version of AIR together with Mac and Windows so all three platforms will have the same release cycle.