This is the list of the universities which offers Best Part Time MBA in US:

Northwestern University (Kellogg)
University of California--Berkeley (Haas)
University of Chicago (Booth)
New York University (Stern)
University of California--Los Angeles (Anderson)
University of Michigan--Ann Arbor (Ross)
University of Texas--Austin (McCombs)
University of Southern California (Marshall)
Indiana University--Bloomington (Kelley)
Ohio State University (Fisher)
University of Minnesota--Twin Cities (Carlson)
Carnegie Mellon University (Tepper)
Emory University (Goizueta)