Well I think the rules need to change and the NCAA needs to expect less $ to allow other venues to host.
Here is my breakdown of neutral venues:
CO: Denver, Loveland
ND: Fargo
SD: Sioux Falls, Rapid City
NE: Omaha, <strike>Ralston</strike>, Lincoln, <strike>Kearney</strike>
MN: St Paul, <strike>Theif River Falls</strike>, Minneapolis
IA: Sioux City, <strike>Waterloo</strike>, Des Moines, <strike>Urbandale</strike>, <strike>Dubuque</strike>, <strike>Cedar Rapids</strike>
WI: Madison, Green Bay, Milwaukee, Milwaukee
MO: St Louis, Independence
IL: Moline, Rockford, Rosemont, Bloomington, Chicago
MI: Kalamazoo, Muskegon, Grand Rapids, <strike>Plymouth</strike>, Saginaw, <strike>Flint</strike>, Detroit
OH: Cleveland, Cincinnati, Toledo, Columbus, Youngstown
IN: Indianapolis, Fort Wayne
PA (Apparently): <strike>Johnstown</strike>, Reading, Allentown, Hershey, Wilke-Barre, Erie, Pittsburgh, Philadelphia
WV: Wheeling
Did I miss anything? Now how many of those are near a university?
EDITS: Updated to reflect building I previously listed that are below the 5000 capacity requirement (struck through) and changed the "too big" arenas to underlined.