My long-term goal of using the PLOTS video spectrometer to identify oil contamination is looking closer than ever recently due to recent tests with a green laser. The above photo shows actual oil residue, dissolved in mineral oil (on the left) fluorescing strongly when shot with a green laser! The right-hand bottle is of mineral oil alone. I haven't yet been able to get a strong reading of this on a spectrometer but will be trying as hard as I can to do so in coming days.
I also wanted to point out a few other uses for spectrometry which have caught my eye. It's always made sense with a long-term, risky project like the PLOTS spectrometer, that we'd have to find other, easier uses along the way. That way, the device and our methodology can be refined in actual use, and we can slowly step towards pollution detection.
Early on, I found a very exciting community of like interest in the Atlanta Reef Club, where Giuliano Moschini made (and dramatically improved) the design to measure the output of coral-growing LED lights. I loved this because a) it treated what I thought was an early prototype as a fully functioning tool, and b) it was being used to test another DIY project -- their modified LED lights. Read more here: http://www.atlantareefclub.org/forums/showthread.php?t=66297
More recently, contributor JoshMC has been measuring lights and other things, but I was very interested to see his post on UV spectroscopy of boiled water, Free & Clear laundry detergent, and bleach. What was neat was that he managed to identify a blue dye in the supposedly "free and clear" detergent! (http://publiclaboratory.org/notes/joshmc/4-28-2012/setup-uv-testing-specrtrometer) The idea of being able to police companies who make such claims using a simple and cheap tool is super cool.
Finally, an early suggestion from a soil researcher named Lucas Patzek was to identify striperust, a wheat disease which is distinctly yellow. Maybe the recent mobile spectrometer as well as the in-progress spectral matching system will make that possible from a mobile phone.