Kaes has been untiringly pushing for optimizations of Rails. Since the
release of Rails 0.12.1, Stefan has lead an effort that made his own
sample application no less than 4 times faster with Rails 0.14.x. Pretty impressive stuff.
Now hes blogging about Rails performance in general at RailsExpress.blog.
So be sure to subscribe to that feed if you care about a faster Rails.
He already has suggestions and benchmarks up on sessions and pagination. [Riding Rails]