In another sure sign that we're marching steadily toward the launch of Windows Mobile 6.5, Microsoft has released the Software Developer Tool Kit, also known as an SDK. From Microsoft's overview:
The Windows Mobile 6.5 Developer Tool Kit adds documentation, sample code, header and library files, emulator images and tools to Visual Studio that let you build applications for Windows Mobile 6.5. ... The Windows Mobile 6 SDK must also be installed in order to use any of the Windows Mobile 6.5 Gesture API or samples.
From what we understand, coding for Windows Mobile 6.5 isn't vastly different than coding for 6.1, so there shouldn't be anything too earth-shattering here. But it does include APIs for gestures -- think flicking and scrolling -- which is new in Windows Mobile 6.5.
The SDK is available in a half-dozen languages, and there are separate builds for touchscreen and non-touchscreen devices. You can download them here.
Update: The WMDev team learns us on Twitter that this is just the 6.5 developer tool kit and you still have to have the full 6.0 SDK.