HTC is currently running a promotion whereby anyone looking to upgrade an eligible smartphone will have the opportunity to get an extra $100 back from HTC with the purchase of a new HTC Tilt 2, HTC Touch Pro2, HTC Imagio, or HTC Ozone.

Here's how the offer works:

Once a new smarthone is purchased, a customer can go to the appropriate site (see below) and enter their specific carrier-dependent promotional code. This will provide them with a mailing label, which they use to send their old smartphone, a copy of the UPC code from the new phone, and a copy of the invoice from the new phone.

After that, they get a $100 check in the mail

See this link for a list of eligable smartphones to trade up from, and the following URLs to get the operator-specific promo codes: here for Verizon Wireless, here for T-Mobile, and here for AT&T. for Verizon

The promotion runs thru December 31st and folks have until January 31st, 2010 to send their information in.