While Windows Mobile 6.5 was officially launched October last year, so far Microsoft hasn't offered an updated SDK (Software Development Kit) for its latest Windows Mobile version. But yesterday, Microsoft silently launched the Windows Mobile 6.5 SDKs which provide documentation, sample code, header and library files, emulator images and tools which can be used with Microsoft's Visual Studio to build applications for Windows Mobile 6.5. The Windows Mobile 6.5 SDK must also be installed in order to use any of the Windows Mobile 6.5 API or samples. It comes with the images for Windows Mobile 6.5 Professional (touchscreen smartphone) and Windows Mobile 6.5 Standard (non-touchscreen) and features different language-sets.
The Microsoft Windows Mobile 6.5 SDK supports Windows 7, Windows Server 2008, Windows Vista, Windows Server 2003, Windows XP and Windows Server 2003 and requires either Microsoft Visual Studio 2008 Professional Edition and above or Microsoft Visual Studio 2005 Standard Edition or above (as always, Express Editions aren't supported).
The different Windows Mobile 6.5 SDKs are now available as a free download from Microsoft.
UPDATE: Something happened to the Windows Mobile 6.5 SDK. While available on Saturday and Sunday, it was removed anytime last night and isn't available as a download anymore. It's not yet clear why Microsoft removed the download but I was told the SDK could cause some problems with Microsoft Visual Studio (which was required to use the SDK). It's most likely (but not confirmed) that an overhauled version will be re-released.
UPDATE 2: Waggener Edstrom, Microsoft's Windows Mobile PR agency just followed-up the SDK-removal and let us know that "on Friday, January 22nd Microsoft prematurely posted a version of an upcoming Windows Mobile 6.5 SDK to a public facing Web page. While the SDK was not announced or promoted, it was discovered and generated questions from the community. The beta SDK has since been removed. To provide the best experience possible for Windows phone developers, the SDK will be reposted once final testing has been conducted. We apologize for any inconvenience".
Cheers ~ Arne