That's a very nice tag, Nick. I've recently realized the importance of keeping all that information about my plants, too.
What i do is keep a spreadsheet with data about each plant, how much i paid, how many i've propagated, what date, etc. It's not really necessary to use a spreadsheet for this, of course, but i have one for my Handera PDA that works well. A database would be better, but i haven't taken the time to find one for my Handera.
By assigning each plant a unique number, you can just put a small tag in the pot itself, and look up the details when you need them. I've recently found a relatively conservation-minded way to label my plants that i'm happy with: i cut out label spikes from the flat sides of plastic milk cartons, and write on them with a small permanent marker.