i just keep a giant spreadsheet, with different columns for stuff like number, birthday, street address, and so on, so i don't have personal experience with one.
However, you may want to check download.com (it's run by CNet). And then search, and filter your results to freeware (and to your OS -- windows/mac/etc).
Since I can't say what is good/bad (since I have no experience with anything like you're asking for) you may want to look at the editor reviews as the regular-people reviews.
One feature I would look for is easy portability -- so that you could easily export what you put in to a text file so that another program can read it (should you decide to change at some point).