I've got one foot in the Linux world (Yellow Dog Linux, running on a G3 iMac. Not that I've figured out how to compile the sourcecode, but I was intrigued enough to download something called Tuxcards - at http://www.tuxcards.de The author describes it as a "hierarchical notebook," although it's hard to tell how deep the hierarchical levels can go. Has anyone any experience with this product?