Hmmm... I've been working in the radiology dept at Hopkins for a year now, which has given me lots of time to chat with people about residency programs. Understand that these are my personal opinions, based on little more than gossip.
So, without further ado, doepug's entirely subjective list of top-tier radiology programs (in no particular order):
Penn
Wash U (Mallinckrodt)
UCSF
Hopkins
MGH
Brigham & Women's
Yale
I'd consider the following programs as being marginally less outstanding:
Stanford
UCLA
UChicago
Duke
Columbia Presbyterian
Of course, if you're considering interventional radiology, you'd be well advised to consider some more programs:
Virginia
Indiana
Oregon Health Sciences Univ.
Northwestern