The past couple of months saw several 3D package updates for IRIX, ranging from the free Blender to Maya.
Blender 2.33a Released May 14th: More Info
Houdini Apprentice 6.5.67 BETA Released May 14th: Download Link
This is actually a beta release - the current version stands at 6.5.83 released May 28th, but there doesn't seem to be an IRIX download. Whether this will change soon or not I have no idea - I posted a query in the forums asking for more information.
Alias Maya 6 Released April 26th: More Info
Note that Maya 6 requires IRIX 6.5.15 or higher. Discussion in this forum thread.
Realsoft 3D 4.5 SP1 Released April 5th: Download Link
We covered this one already but it deserves to be up here with the rest. More information and feedback in this forum thread.