I highly recommend not only checking out http://freeware.sgi.com but also pages on the Other Sites page for other software.

In particular, please drop a quick email of thanks to the people on freeware.sgi.com who continually make available pre-packaged freeware for IRIX. Without them we'd all be a lot worse off.

All applications on here have been compiled using GCC under IRIX 6.5 on my Octane.

Root disk cloning script

The XLV/XVM plexing option is expensive - very expensive. Yet everyone needs a backup of their root disk. This korn script can be run nightly from cron, and will clone your root disk. All you need is another disk in the machine, which has already been partitioned by fx, and away you go!
The script is pretty straightforward, so can easily be modified to clone other important disks in your machine.

Quake, Quake2, and mods

Dug out from an old backup tape, here's my mirror of the SGI Quake pages from SGI's website. Quake, Quake2, plus some entertaining mods like Action Quake 2.

Allegro

Allegro is a cross-platform gaming library - similar to SDL. Off the top of my head, you'll need ESD installed to get sound. There's an ESD tardist on the SGI Freeware website.
The Allegro homepage can be found at http://sunsite.dk/allegro

Elite:TNK

Elite is the greatest computer game known to man. Ever. Elite:TNK is the result of a project by Christian Pinder to reverse-engineer Elite from the original BBC disk version.
This requires Allegro, and runs splendidly on my Octane. It installs in /usr/local/elite-tnk, and the binary (newkind) must be run from within there.

The Elite:TNK home page used to be found at http://www.cjpinder.clara.net/elite.html, but this site now appears to be dead.

ActX

ActX is a collection of anime window sitters (Active X Window System).
The home page can be found at http://kurumi.sakura.ne.jp/~chimari

AkaneClock

AkaneClock is an excellent anime clock. Lots more fun to have sitting on your desktop than the normal clock.
The home page can be found at http://kurumi.sakura.ne.jp/%7Echimari/ActX

aterm

aterm is my preferred terminal. It allows background transparency, and with the Buffy GTK theme fits right in with the Indigo Magic desktop.
The home page can be found at http://aterm.sourceforge.net/

PRNGD

PRNGD is the Pseudo Random Number Generator Daemon - a source of entropy. You'll need a decent source of entropy for any cryptographic applications - OpenSSL, for example. PRGND saves any entropy it has when it's shutdown - this means you have a strong source of entropy right from when your machine boots. It also doesn't generate a 'pool' of entropy, so, unlike EGD, it can't be drained and won't block.
The home page can be found at http://www.aet.tu-cottbus.de/personen/jaenicke/postfix_tls/prngd.html

GnuPG

GNU Privacy Guard is an OpenPGP compliant Open Source replacement for PGP. Personally, I've used PGP 2.6.3i for donkeys years, but more and more software appears to be written to use GnuPG specifically - hence this tardist. This version isn't the most recent, but works fine for me. I may build a newer tardist sometime if there is enough demand.
The home page can be found at http://www.gnupg.org/

zlib

zlib is a compression library. Pretty much anything that will use compression will need this. This version fixes some potential security flaws with previous versions. Note that any applications statically compiled against older versions will need to be re-compiled against this new version to use the fixes.
The home page can be found at http://www.gzip.org/zlib/