Just about the most hyped handset to come out of the Mobile World Congress in Barcelona earlier this year, the Sony Ericsson Xperia X1, a white labeled HTC phone, comes equipped with a hiptop-style slideout keypad that has a gliding 
motion to it. The device runs Windows Mobile 6.1 but manages to cover up the OS with a number of user-selectable custom skins--including one for Google users and one for world travelers. The UI runs on a 800 x 400 resolution touchscreen that was running slowly during our demo at CTIA, but Sony Ericsson has yet to announce a release date for the handset outside of "late 2008."
For more on the Xperia X1:
- see this photo slideshow