It's donationware, not freeware, but I think
GrandPerspective deserves a mention because of the unique and beautiful manner in which it presents its results; ...lots of neat themes, too.
(It's working fine for me in !0.5.7 with the exception of the keyboard "Re-scan" command; a bug report has been filed.)
Edit: The grand perspective continues on the developer's "Donations" page which offers options of $5, 10, 20, 50, 100, and 250.