FSL is a comprehensive library of analysis tools for FMRI, MRI and DTI brain imaging data. It runs on Apple and PCs (both Linux, and Windows via a Virtual Machine). Most of the tools can be run both from the command line and as GUIs ("point-and-click" graphical user interfaces).
To use FLS, set up the environment varibles as the following (e.g., add to the .bashrc file)
$ export FSLDIR=/gpfs/research/software/FSL/6.0.2/install $ export PATH=/gpfs/research/software/FSL/6.0.2/install/bin:$PATH