AIX tricks
AIX is IBM's UNIX. It is weird but delightful. Unlike Solaris it's small, but, also unlike Solaris, it somehow manages to have usefull stuff anyway.
Installing
Install 5.3, then upgrade it to TL7, then to the latest service pack level. Go here: http://www-933.ibm.com/eserver/support/fixes/fixcentral/pfixpacks/53 then download the most recent Technology Level (5300-07-00-0747 currently) then 5300-07-03-0811 or whatever. Warning, huge downloads. TL7 is like 1.8G and 5300-07-03-0811 like 260M.
Many things that are broken in 5.3 are fixed by these updates, like topas(1) and X11 ssh forwarding and various other things you may want to use. So do it.
Freeware
(Mostly free software, but SGI and IBM and stuff likes to call it freeware, because they're giving it to you for omgnomoney).
The list they have on their website is outdated, you will find newer versions of some things on this super secret ftp address: ftp://ftp.software.ibm.com/aix/freeSoftware/aixtoolbox/RPMS/ppc/
Yes, they're distributed as RPM. No idea either.