In no particular order:
Number of hearts (cases, not transplants)
OB volume (=epidurals)
PEDS volume (Need numbers to graduate residency, even little itsy bitsy ones)
Didactics (should be there and be good)
Transplants (esp. LIVER)
Size and/or use of CRNA's, size of residency that is...Basically you need time to read/have a life. CRNA's will give you this at smaller places. Larger places may have enough residents not to kill you. Basically if you are 4-5 per class without CRNA's, you're screwed if the surgeons operate much.
ICU - This will be more important in the future when all programs go 4 years and extra ICU months will be required.
Other NICE stuff:
Regional - probably every programs weakness except for a select few!
Simulator - Not that many in the country actually.
Name - This will get you that great fellowship or job. Realize though that as the competition grows, some competitive people will end up going to some 'crap' programs. These programs will in turn get better as better people go through and they attract better residents, then faculty. Just remember that name does not equal volume and numbers do equal graduation from residency. You need numbers. Follow the numbers.