I am a College fan, so here goes:

MLB
The old Fulton County Stadium
The old Baltimore stadium

NBA
Old Hemisphere arena (San Antonio)
New San Antonio arena (minor league hockey as well.)

NFL
Never been to one

College FB
University of South Carolina Williams Brice Stadium
UVA, Charlottesville
Gator Bowl
Michie Stadium, West Point
RFK Stadium (NFL stadium, but I was there for the Army-Navy game)
Clemson
Presbyterian College (SC)
UT, Austin
Texas Tech, Lubbock

College BB
West Point, NY
University of South Carolina
Charlotte, NC arena. (Pro arena, but for a college game)

College Baseball
University of South Carolina
West Point, NY

Minor League Baseball
Columbia, SC
San Antonio, Tx
San Angelo, TX

College Hockey
West Point, NY

Swimming Venues
Munich
Georgia Tech
(included because the both hosted the Olympics. I was there because my daughter is a competitive swimmer and competed there, not during the Olympics though )