Just writing something about hierarchy visualisations and found these two useful apps.
GrandPerspective using (cushion) treemaps [1]. Similar Disk Inventory X.
diskring using sunburst, multi-level pie chart or ring(s) chart (not developed any more) [2]. Similar is DaisyDisk.
[1] Van Wijk and Van De Wetering, Cushion treemaps: Visualization of hierarchical information, IEEE Symposium on Information Visualization 1999 (Info Vis’ 99) Proceedings, 1999
[2] Stasko, Catrambone, Guzdial and McDonald, An evaluation of space-filling information visualizations for depicting hierarchical structures, International Journal of Human-Computer Studies, Elsevier,2000
