If you have are running a custom ROM that has Sense UI (AKA Touch Flo 3D 2.5) as its main user interface, there is now a cab available that allows you to enjoy the glories of landscape mode.
Previously, Sense UI has only offered a Portrait-only point of view as the device that it originally runs on, the HTC HD2, does not have a slide-out keyboard and therefore does not require a landscape mode.
You can go to XDA and download it here. Please note, there are some issues known with this release, including the Calendar page having some display issues and the retractable slider button may whiten out at times. Also, you must install Mortscript and follow the guidelines in the post. Below are the steps required to perform this hack. All required files are located in link posted above. If you are a ROM Chef, he has included files so that you can bake this into your next ROM.
STEP 1 -INSTALL MORTSCRIPT 4.2
STEP 2- DISABLE MANILA
STEP 3- INSTALL MY CAB
STEP 4- INSTALL SMALL REG TWEAK (CAB)
Source- Pocketnow.com