Information Visualization Benchmarks Repository (Includes the benchmarks for InfoVis contests 2003, 2004, 2005, 2006 and VAST contest 2006):
http://www.cs.umd.edu/hcil/InfovisRepository/index.shtml

A more updated one:
http://hcil.cs.umd.edu/localphp/hcil/vast/archive/provenance.php

MISC:
The full database of IMDB
http://www.imdb.com/interfaces

DBLP (From the project page of Andrew W. Moore's Machine Learning course in Fall 2005)
http://www.cs.cmu.edu/~awm/10701/project/data.html#C:_DBLP_Research_publication_database_