Ask HN: Keyboard shortcuts in web applications

I am looking for good advice on implementing keyboard shortcuts for web applications.

Unfortunately I'm drawing a blank on finding a standard set of expected behavior (although quite a few people recommend just copying gmail). Technically Firefox will let you emulate a desktop application pretty well, but IE and others won't, so options are pretty limited.

Has anyone found a good set of data about what users do/don't expect from heavy web applications and keyboard short cuts? Is it OK to accept that only power users will be working with shortcuts and bind things like ]-c as copy?

Right now I'm thinking of binding ] to bring up a shortcut options overlay that looks like http://revis.co.uk/shortcuts.png