A substantial portion of the SDSS-III software is written in the IDL language. We strongly recommend installing the idlutils package, as this is a prerequisite for many other SDSS-III software packages.
The basic software tools necessary for analyzing SDSS data are contained in the IDL-based products:
photoop. The latter two often depend on two more products containing essential meta-data:
Additionally, there are a number of products distributed with the software that contain external data of various sorts (dust maps, FIRST catalogs, RC3, Tycho-2, etc).