Good question, actually. See the link for some answers from the /. community:
Leemeng writes “I’m looking for a simple, free, and F/OSS flat-file database program. I’m storing info about Wi-Fi access points that I come across, maybe 8-9 fields per entry. I’ve outgrown Notepad. This info is for my own reference only; it is not going on a Web server. Googling was unhelpful, with results skewed towards SQL, Access (MS), and Oracle, all of which would be overkill for my purposes. My criteria are: it must be simple, F/OSS, must work in Windows Vista, preferably use a portable format, must not be an online app, and must not require Java. Does such a beast exist?”
(via http://developers.slashdot.org/article.pl?sid=08/05/20/2150246)
Williamo's Blog 