Ruby
Links - Ruby Rule Engines
Updated Sept 19 2008: more links for Ruleby
Not a major category among the many rule engines implemented in Java and other languages, but some of the implementations are solid and interesting.
In fact, Ruby rule engines are particularly interesting because my hosting service ( Hostmonster ) provides them as installable Ruby gems. The Radiant CMS is also available as an application platform to connect the rule engine to the outside world.
Links- Ruby Language
Updated Dec 14 2008: link for Ruby Shootout
Some useful links.
Some good advice from railshosting.org about setting up Rails in a shared hosting environment, and Rails hosting in general.
See Hosting a Ruby On Rails Application on HostMonster.Com in 8 very easy steps, answering such burning reader questions as:
