An article at How-To Geek explains how to create keyboard shortcuts for Google Chrome. It explains the built-in way to assign a keystroke to an extension, and recommends the Shortcut Manager extension that lets you create shortcuts for much of Chrome’s built-in functionality.
I will take this occasion to recommend Tab Rocker, by Joel Weinberger [twitter:metromoxie]. It lets you toggle between two open tabs via a keystroke. Joel wrote the first draft of it in a Thanksgiving afternoon after I whined about not having that functionality. Shortly afterwards Joel began working at Google as a security genius (which is not his official title but should be). And, yes, he is related to me: he’s my nephew.