From thingiverse pages:
This spectrometer is a scientific tool that straps onto an Android or iOS phone, tablet, or any camera capable of focusing very close (macro-mode) and allows you to collect spectra. Why would you want one? You can use it to identify the elemental composition of things (light bulbs, olive oil, beer, etc) based on the colors of light they emit. You can even use it to monitor your home brewing progress (http://bit.ly/Xyor6B).
http://www.thingiverse.com/thing:49934 (version 3)
http://www.thingiverse.com/thing:125428 (version 4)
Here is video describing their idea and scenarios for using DIY spectrometer:
They had a successful Kickstarter campaign:
Spectral workbench is a place to archive, share, and interpret spectral data.
Different model of 3d printed spectrometer:
You can also build 3d printable DIY Raman spectrometer: