A great open-source spectrometer built the same way is available from PublicLab here: http://store.publiclab.org/products/desktop-spectrometry-kit... (or you can just build it yourself using their designs on the Wiki). PublicLab also has a repository for spectra so you can calibrate and compare with others.
You can also buy diffraction glasses for under $10. They're marketed as "rave" accessories, but I found them useful for quickly identifying incandescent light bulbs hidden inside fixtures, in order to replace them with CFLs.
Or just get diffraction gratings. No need for the silly "glasses" markup, you know the number of lines per millimeter, and you can get 25 of them for around the same $10
This looks great! I'll try this with my kids soon - I try to do at least one experiment every week...
This did for some reason wake a bit of nostalgia in me from the earlier days of the public Internet. I bet it's the spartan design and the lack of anything else other than the to-the-point content. (That said, fascinating content - might try it out!)
Just made one this morning after reading the article. Super easy and works like a charm! What fun
If you combine this with a bit of numerical post processing and some calibration with a laser pointer you can get a pretty precise result. We did this in university, it was fun :)