As anticipated Microsoft unveiled Windows Mobile 6.5 at the MWC 2009 today.
The new Windows Mobile 6.5 honey comb home screen keeps people up-to-date on important information by providing a dashboard-like experience to items such as new e-mails, texts, missed calls and calendar appointments.

Windows Mobile 6.5 also includes an improved touch-screen interface, making it easy to take action with a finger, and an updated version of the latest Internet Explorer Mobile browser, which in a third-party research study sponsored by Microsoft supported execution of up to 48% more assigned tasks than the other browsers and phones studied.
The new operating system features Windows Marketplace for Mobile, a rich and integrated marketplace for searching, browsing and purchasing mobile applications from Windows phones or from a PC by simply using a Windows Live ID.
The new marketplace will be included with all Windows phones based on Windows Mobile 6.5, which will help consumers to easily find, install and experience those applications that fit their needs and make the phone truly personal. Developers, who have already built over 20,000 applications for Windows phones, will be able to offer applications to customers through the marketplace via a simple security and compatibility check from Microsoft.

The new Windows phones running Windows Mobile 6.5 are expected to be available in the second half of 2009.
Via this Microsoft announcement.