Pretty sure we already had this thread.
Maybe Eddie Sutton @ OSU (after KSU passed on him)
I'm sure there have got to be other examples. Probably there are several coaches who were "pressured out" rather than fired, like Tubby at UK or Dana Altman at KSU (though Altman doesn't fit the mold of this question, because he went to Creighton next).
If you are sure about others, give em up. I'll even take "pressured out" ones. Sutton is probably a gray area (more likely was pressured to resign due to the scandal), but I will include him on the list.
So far:
Sutton from UK to hapless and moribund OSU (clearly OSU is on a lower level than UK, and they were struggling pretty bad so it was worth a risk to hire the hometown guy)
Smith from UK to hapless and moribund Minnesota (clearly Minnesota is on a lower level than UK)
Weber from UIUC to recently revitalized KSU which was actually more successful than UIUC over the past few years.
Smith from Minnesota to hapless and moribund Texas Tech
Wow hiring a coach who has just been fired for being a bad basketball coach looks like a great sign of a program's health!