perlfMRI is a very simple tool I created for viewing functional MRI data, written entirely in perl. What's nice about it is that it lets you simultaneously view three planes through the brain and to rotate them in 3d (see screenshots below).
It requires that you have installed the Perl/Tk module, as well as the Perl Data Language (PDL). Your PDL install must include TriD. PDL with TriD compiled nicely on Mac OS X 10.4 (Tiger).
Currently, perlfMRI only opens data in ANALYZE format, but I will update it soon to read NIfTI as well. Also coming soon, the ability to overlay more than one functional image at a time, and online conversion to standard space coordinates.
Click here to download perlfMRI
(These images are showing my own brain, overlayed with activations in my auditory cortex while I listened to music.)