Today I found a great command in Pathogen.vim, :Helptags. This is a riff off :helptags {dir}, a Vim feature that builds helptags for directory {dir}.
:Helptags does the same for all the directories in your runtimepath, which defaults on Unix and Mac OS X to:
"$HOME/.vim,
$VIM/vimfiles,
$VIMRUNTIME,
$VIM/vimfiles/after,
$HOME/.vim/after"
The use case here is when you've just loaded a new plugin into your Vim bundle, you open up Vim, and :h {my_new_plugin} isn't 'helping' you out.