To add regular expression support (only case-sensitive at this time, case-insensitivity will come later) the only code I had to write was the below:

module ActiveRecord::Extensions

  # The below supports finder sql for regular expression 
  # support the PostgreSQL adapter:
  # Example:
  #    Model.find :all, :conditions=>{ :title => /regex/ }
  #
  class RegexpPostgreSQL < AbstractExtension   
    NOT_EQUAL_RGX = /(.+)_(ne|not)/

    def self.process( key, val, caller )
      if val.is_a?( Regexp )
        match_data = key.to_s.match( NOT_EQUAL_RGX )
        key = match_data.captures\[0\] if match_data
        fieldname = caller.connection.quote_column_name( key )
        return Result.new( "#{caller.table_name}.#{fieldname} " +
             "#{match_data ? '!~ ':'~'} ?", val )
      end
      nil
    end

  end
  register RegexpPostgreSQL, :adapters=>[ :postgresql ]

end

I am really digging the pluggable extensions so far. What do you think of the above code set to add Regexp support for PostgreSQL?