Keypress is an input capture library with some very special features, it is easy to pick up and use, has a reasonable footprint (~9kb), and has no dependencies.
Mousetrap is a standalone library with no external dependencies. It weighs in at around 1.9kb minified and gzipped and 3.5kb minified.
jQuery Hotkeys lets you watch for keyboard events anywhere in your code supporting almost any key combination.
Keymaster is a simple micro-library for defining and dispatching keyboard shortcuts in web applications.
Jwerty is a JS lib which allows you to bind, fire and assert key combination strings against elements and events. It normalises the poor std api into something easy to use and clear.