It looks like it's pretty official at this point. Joe Smith reports on his blog:
Hammel said he has been informed by the Rays he's been traded to the Rockies. Though he was appreciative the Rays gave him opportunities, Hammel is looking forward to a fresh start in Colorado, where he hopes to be a part of their big-league rotation.
He figures to get some opportunity to crack the rotation this season, it will be up to him to make the most of it. Heading back to Tampa will be Aneury Rodriguez, as previously speculated
UPDATE: The report is coming down several pipes now, Tracy Ringolsby was one of the earliest to say that it's official.