Google's released a early access SDK for their Android Mobile Phone OS. I've only had a few minutes to play with it but I'm already impressed. Google's removed a lot of the initial barriers developers face when starting out with a new platform There's none of the "register as a developer, wait for us to send an unlock code for the free emulator" (yes Nokia, I mean you) or give us a pile of money (Microsoft) for an IDE that doesn't work for mobile development without major tweaking. Everything you need to get started is at code.google.com/android/. Anyone can just download the Android SDK, no need to register or anything. Additional points to Google for making the SDK available on all three major desktop platforms (Max OS X, Windows XP/Vista and Linux Ubuntu) from day 1.
I know a lot of people are disappointed that it's "just" a Java SDK. Still for a first release it's very polished, with a functional emulator including a working browser and Google Maps and some very readable documentation. There is a plugin for the open source Eclipse development IDE. But you don't even need Eclipse to play with the emulator. Just download the SDK, extract everything from the zip, run tools\emulator.exe and in less than 5 minutes you are up and running! To help you get started Google has nice tutorial, sample code and a very active Android Developers Google Group. There's also a lively independent Android development site at ohadev.com.
The emulator is running actual Android ARM binaries on top of a ARM emulation layer. It seems fast and stable on my low spec PC (XP, 2.4 GHz Pentium 4, 512 MB ram) giving the impression that the Android OS is in nearly ready for deployment.
Google has promised to release source code for the full OS but it looks like they will not be supporting development in C++ or any language other than their Dalvik variant of Java. Once the full source is released I bet the big Linux developer community will hack in support for C++, Python and Mono and get Android running on existing hardware like Treos, Ipaqs the N800 and the Neo. I've never been a fan of Java (slow on the desktop, Java ME's onerous signing and security model and the high cost of hosted Java web server envronments) but Android could change my mind.
There will be lots of people playing with Android as Google is running a contest for the best Android applications with $10 million in cash prices, including $275,000 for each of the top 10 apps.