again not foss so won’t dwell at length — but i use fund manager from beiley software. commercial, but works double-entry and handles more investment complexity than a human could ever need. windows app, i run it under wine on linux and crossover on mac. (i don’t own a windows box — that’s how irreplaceable it was for me.)
i’m shopping for mp3 players for precisely this reason - a friend has an ipod touch that abruptly stopped scrobbling. the last.fm app is stuck in a loop sucking battery. and she needs bluetooth anyway. she has always kept music and phone separate but now we have to ask the five whys on that before getting her a new unfamiliar gadget.