HTC has added the HTC Desire Z, ChaCha, Aria, DROID Incredible, Status, and T-Mobile G2 to their growing list of officially unlocked devices. Some of these devices have already been unlocked by the Android community, but this is an official and safer way to unlock your bootloader.
The HTC Dev program requires five-steps to unlock your device. HTC strongly suggests that you do not unlock the bootloader unless you are confident you understand the risks involved. Unlocking your device could cause damage to your phone that is not covered under the warranty.
If you are not worried about the risk, you can head to HTCdev.com and get started. For a list of other avlable devices, check the supported list device on the right hand side of HTCdev.com.