Comment KeepNote (Score 1) 170
The best app I have come across for storing ideas is KeepNote. Free and cross-platform, though it could do with a few more features. OneNote seems not bad for storing recipes etc, but is obviously unacceptable for storing personal data.
In terms of PIM, this is not really the same as OP was asking as most of them are calendar/to-do based. I've tried every single ones of these, and have found MyLifeOrganized to be the best. One of the few apps I've been happy to pay for. Microsoft Windows only but works under WINE.
Phillip.