The Cell Phone Spectrometer is far from the only way to become familar with spectroscopy. Here are some links to work by other people.
Mitch Nelson "Dr. M. C. Nelson" <email@example.com> put together a program in C that did much of what the cell phone spectrometer does, but did it 5 years before the CPS was released. Here's a .zip of his work, version of December, 2010. Want the latest version? Go here: http://www.materialintelligencellc.com/mitchnelson/WinSpec/.
Simon Quellen Field <firstname.lastname@example.org> has published related work in Make magazine. Look at what he's done here http://www.make-digital.com/make/vol24?pg=60#pg60 and the succeeding page.
Mathew Lippincott has a different variety of home-built spectrometer at http://publiclaboratory.org/tool/spectrometer. There's a facility there for collaborative spectroscopy.
Following publicity about the CPS in October, 2010, people started developing apps for the iPhone and Android to do what the .exe file on this website does.
Dave Bomberg has posted a native app for Android. The software is now totally in the phone! Android version: LearnLight . He notes:
The user has to take pictures with their built-in camera application first, then import the photos into my app. (or use any of the 4 example images I include as a sampler). ===================================
For additional documentation, go to the Android link.
In May, 2012, Bomberg also released an iPad version of the software, limited to using previously obtained data (i.e. you can't add your own). Just go to the iTunes store and search for "LearnLight."
Check your provider to see if they've posted Apps for other platforms.