i just found this when i google search about ruby and openwrt:

http://www.tienshiao.org/archives/2006/01/03/ruby-on-openwrt/

theres a link there on a binary file ruby. i placed int in my /opt/usr/bin and i can run ruby scripts now in openwrt!

i hope someone could come up with ruby on rails installation for openwrt. that would be sweet if openwrt can serve RoR pages!