The biggest problem for HTC Touch HD owners is the lack of a d-pad. Tirinoarim from xda-developers just created an application that could minimize this, with the help of the on board accelerometer.
You basically tilt the device to move the cursor, or scroll a list to a certain direction. The application although still in beta form, works on Touch HD only with minor problems (It could also work on Touch Diamond or Pro).
If you want to try out GPad on your Touch HD, you can find the application and instructions here.