Developing for the Blackberry Playbook will Rock
At MAX we were shown, in a glass case, the new Blackberry Playbook. I am personally super excited to try it out and start developing for it. First, you build apps for it using Flash (pure ActionScript or MXML), second, their store will be free (at least for some introductory time) and third, the hardware specs makes it the best on the market (1 GB RAM and 1 GHz dual-core processor??). Interestingly, their first development platform for it is Flash, and they said that later they will allow you to use Java and C++, so you can imagine that at this moment, Flash is as good as native.
And there is more. If you develop an application before the Playbook's launch and it gets approved, you'll be able to get a free Playbook from RIM. The launch date is not yet announced, but I would get started as quickly as I can.
There are weekly webcast series you can attend. Those are hosted by RIM and usually Renaun Erickson from Adobe also shows relevant ActionScript code. They are a good starting point. You can find the link to those, the Getting Started guide and the documentation at the BlackBerry Tablet OS Development Resources.
What are you waiting for?