http://jgoodies.com/freeware/jdiskreport/index.html
JDiskReport is a system filespace analyser, that is part of a demo of the jgoodies.com system.
For functionality and ease of use it scores highly with a strong comparison to SpaceMonger without the treemaps. I like its multiplatformness, abiltity to exclude directories (useful for symlinks) and its freeness.