For the "to do" list, expand-ahead browsing looks like a useful approach to build upon PygmyBrowse (see my live demo). The approach is described in "Expand-Ahead: A Space-Filling Strategy for Browsing Trees" by McGuffin et al. (doi:10.1109/INFOVIS.2004.21, PDF also here). There is a video on Ravin Balakrishnan's site, which is an AVI file that I haven't bee able to coerce my Mac into playing, hence I've posted it on YouTube.