The guys over at NeverBlock have released a database adapter for Rails application that will severely increase the performance of ActiveRecord. Its also really easy to integrate into your application. Heres how: Add a line to environment.rb for mongrel or thin servers:
require 'never_block/servers/thin'
or
require 'never_block/servers/mongrel'
Change the adapter in database.yml:
adapter: neverblock_postgresql
or
adapter: neverblock_mysql
You can also specify the number of connections (default of 4):
connections: 12
More information, along with benchmarks, can be found here.