With much hassle and heartache we have finally managed to get Ruby on Rails working on AIX, complete with a connection to an oracle database on another box.
Currently we are using Webrick in production mode with rails doing much of the caching work. But the performance is very good, and as we are only powering an intranet with 3000 users things are fine.
The two pages below are one of the keys to sucess. The other is someone who understands GCC, and has some time to spare.
http://homepage.mac.com/cjgibbons/rubyonaixhowto/t1.html
http://homepage.mac.com/cjgibbons/Downloads.htm
Big thanks to Chris Gibbons who took the time to put together the walk through.