You can cache static pages by using caches_page class method of Action
Controller. It is also possible to cache only part of the page that is
static while leaving the dynamic sections out by using fragment
caching in Rails.
When you are under situations where you cannot cache due to security
reasons you can use Action caching, this will be slower but that is
the price to pay for enforcing security. Another cool way to speed up
is to use memcached. You basically use a machine with lot of free
memory as your cache server by installing memcached. The client must
also be setup to connect to your server.
All these tricks are explained in Rails Cookbook.