IHelp lets you view and search the documentation of an object from Ruby.

sudo gem install ihelp

Now with full text search over installed help, powered by Ferret.

"How do I justify a string?"
ihelp 'justifying strings'
ihelp 'How do I justify a string?'

"I need to read little-endian ints from a string"
> String.help 'little-endian int'

"Hmm, how did String#unpack work again?"
> String.help:unpack

"What is this object and what can i do with it?"
> object.help

"Someone told me that I should look up Mutex#synchronize... but I don't have that loaded."
> help "Mutex#synchronize"