I came across a program called "Aquarium Manager" to help keep track of water parameters and observations. It's got some neat stuff, like graphs, analysis, and conversions. There are a couple of things about it that I'm not thrilled with (like not being able to maximize the window), but since it's free, I can't complain too much!
If you're interested, send me a PM with your email and I'll send it to you! (1MB file)