There is no such thing as a national list of open radiology spots. Unless you want sit out a year and try your hand in the match for a PGY2 spot, you've got to do a lot of leg work. Be proactive, NOT reactive:
PROactive:
The best, but least convenient way is cold calling every program you are interested in (and even not interested in), introducing yourself in an unobtrusive manner and leaving your CV. Talk to the radiology PD and Chairman at your institution. Rarely you can get an insider tip at your institution about expanding a spot or that a resident has to take leave for family reasons.
Reactive:
By the time someone posts an opening on Auntminnie.com, usually its already too late.
If you want it bad enough, and you're willing to work for it, you can find a spot.
Good luck