Keyboard Shortcut to Submit Current Form on Chrome/OS X?
Thanks to Lri's comment above, I've been inspired to fix this for myself. I've written a Google Chrome extension that will use the alt+shift+s keyboard shortcut on Windows/Linux and cmd+shift+s on Mac to submit the form currently being filled in. Using it now to lazily submit this answer :D
http://neosmart.net/blog/2011/google-chrome-form-quicksubmit/
More than five years later, surprisingly no one else has implemented a similar solution so it's (finally) been published to the Chrome store and is available for installation/download.