Kudos to Jason Langridge for this one.
Windows Mobile 6 emulator images are available for download from Microsoft. You will need the emulator installed on your machine, with the various networking components etc.
Unlike the previous SDK images, these work in the standalone emulator.
The emulator is ideal if you are looking at Exchange 2007 as you can see the extra features of Windows Mobile 6 when used with Exchange 2007 and test the auto discover functionality that Windows Mobile 6 provides.
You need version 2.0 of the emulator for these images.
185mb for the Professional version emulator. Watch you get the correct language.
Emulator 2.0 download:
Windows Mobile 6 images: