Leigh asked:
>I was looking at the list of drivers supported by rails, and it is
> missing out a lot of databases.  As good as rails is, its a non-started
> in my company as it doesn't support any of our enterprise databases.
>
> If someone wanted to develop a pure ruby driver for rails, where would
> they start ?  Is there a developers guide ?  Is there a ruby-jdbc
> bridge ?

The Rails wiki is a good source of this kind of information, as are:
* #rubyonrails on IRC
  * irc://irc.freenode.org/rubyonrails
  * (complete logs) - http://saqataq.us/rubyonrails/
* the Rails mailing list
  * http://lists.rubyonrails.org/mailman/listinfo/rails
  * (archive) - http://thread.gmane.org/gmane.comp.lang.ruby.rails/

Try the following Rails wiki pages specific to your question:
http://wiki.rubyonrails.com/rails/show/HowToWriteAnActiveRecordAdapter
http://wiki.rubyonrails.com/rails/show/DatabaseDrivers
http://wiki.rubyonrails.com/rails/show/HowToUseRailsWithoutADatabase

Cheers,
Dave