Excellent. You may wish to mention that the default Rails.cache is a per-process cache and doesn't work between instances / goes away at process death.

For Memcache users, configure Rails.cache to use Rails' built in :memcache_store:

http://api.rubyonrails.org/classes/ActiveSupport/Cache/MemCa...

For Redis fans, try :redis_store:

https://github.com/jodosha/redis-store

This covers Rails 3 caching pretty well:

http://broadcastingadam.com/2011/05/advanced_caching_in_rail...

Note for Rails 2: If I recall correctly, in Rails 2 fragment caching/action caching still uses the filesystem even if you have a cache_store set.