The release of Windows Mobile 6.1 brings a number of improvements for users but retains the same SDK and libraries as 6. The devices ship with .NETCF 2.0 SP2 in ROM.
This release adds additional screen resolutions to both the Professional (touchscreen) and Standard (non-touchscreen) editions. For Standard edition these are all 131 dpi and consist of 320x320 square and 400x240 and 440x240 landscape. For Professional there are 240x400 and 480x800 portrait screens. Once again these additional screen sizes emphasize the importance of making sure your app dynamically adjusts to make best use of screen space, for example using the Windows Mobile Line of Business Accelerator 2008.
The images (currently US English only although localised versions should follow) are available to download here:-
http://www.microsoft.com/downloads/details.aspx?FamilyID=3D6F581E-C093-4B15-AB0C-A2CE5BFFDB47&displaylang=en