Looks like HTC jumped a new member into the unlockable bootloader gang this morning: the EVO Design 4G. The Design now joins the ranks of the Sensation, EVO 3D, and Flyer in the realm of unlocked bootloader-dom, along with another recent newcomer to the scene, the Amaze 4G on T-Mobile.
As always, the process will void your warranty, but if an unlocked bootloader is what you're after, then this is the place to get it done. The process is pretty simple and easy to follow, so, if you're feeling froggy, head over to HTCDev to get started. Good luck!