For MD programs, I would check out FREIDA (ama-assn website) first. From there you can see all the programs possible and begin to trim down your selections.
As pointed out above, location is probably the first factor I would go on. From there you can further eliminate programs based on size or other factors listed on FREIDA.
From there, the best source is each programs website. I also used
http://radiology.matchapplicants.com/ -> Select program link -> Browse schools to look at the comments sections. Obvious reporter bias and some data is outdated/limited but should be able to see if there is a blatant reason to avoid applying.
I think the WAMC thread mentioned is a good idea, but really you should apply very broadly regardless. Interview invites can be a fickle thing and the only thing at the end you should worry about is if you have enough interviews because that is something that isn't easily fixable after initial apps go out. An extra couple hundred dollars is not worth the risk of NOT matching.
Lastly, ask your home PD or mentor. If there is a resident you are close with you can bounce program names off them as well.