Is there a way  to schedule hibernate/shut down on an HTC Desire HD? I'm planning to get SleepPhones, a sort of comfortable headphone which I plug into my HTC Desire HD. I would play music which puts me into sleep (hopefully) for up to 60 minutes.

Is there a way hibernate/shutdown the phone say after 90 minutes or perhaps at 2am every day to save power?
You should be able to use either Locale or Tasker to setup a condition (i.e., at 2 am) to do something (turn volume down, stop media player, or turn off wifi or other services).  But as far as I know, neither program will let you shut down your phone.