You learn something new every day! LED as (probably not great, but acceptable) light sensor. Heck, looks like there's even a Wikipedia page on it.

Sucks that a lot of the lower-wavelength (blues, greens, whites) have such a high forward voltage, and really low reverse voltage tolerance.

Maybe use one of these to charge up the internal A/D and sample briefly?

Just like rootbeer, they're so bubbly, and cloying, and... Happy. And the worst part is that if you drink enough of it, you actually start to *like* it. Paraphrased from Quark and Garak

For that price, you're looking at quite used (and possibly of questionable calibration / shape--or from someone offering a family / friends discount). But if you're a hobbyist, you could always build your own using a computer, a microcontroller with an A/D and a serial / USB interface, and a graphics package. I believe you may also be able to find some USB-based ones that are basically what I described previously in the back of Circuit Cellar or some such.