Here is a 'scorecard' by conference for 1995, the third year of data I have for this. I thought this might be useful info since the regionals are a major source of inter-conference and inter-region play that helps determine the relative strength and hence future seedings of teams from various regions and conferences.
Here is the 'histogram' of the success rate for the 1995 NCAA regionals.
------ wins ------
Conference Number 0 1 2 3+ champ comments ...
========== ====== === === === === ===== -----------------
SEC 6 1 2 3 1 good showing by 5 teams
ACC 4 1 1 2 solid performance
SWC 4 1 3 close but needs Big-8
Pac-10 3 1 2 solid performance
Colonial 3 1 1 1 deserves 3 teams?
SunBelt 3 2 1 " " "
Mo-Valley 3 1 2 " " "
Big-8 2 1 1 wait 'til Big-12 !!
Big-West 2 1 1 underrated?
Big-East 2 1 1 still need Miami
TransAmerica 2 2 better than some
Ind-Miami(FL) 1 1 they're back again!
Big-South 1 1 playin team does great
West Coast 1 1 was playin last year?
WAC 1 1 weak
Metro 1 1 weak
Southern 1 1 two slots last year
Southland 1 1 " " " "
MAC 1 1 " " " "
Big-10 1 1 pretty bad showing
Ohio Valley 1 1 playin
Patriot 1 1 playin
Atlantic-10 1 1 playin
Mid-Continent 1 1 playin
Ivy 1 1 playin
Metro Atl. 0 -lost playin
MEAC 0 -lost playin
Midwest Coll 0 -lost playin
Northeast 0 -lost playin
N. Atlantic 0 -lost playin
SWAC 0 -lost playin
Great Midwest 0 --ignored