The Chrome Web Store has in-depth documentation on preparing an app for submission, including details about the manifest file, at https://developers.google.com/chrome/web-store/docs/get_started_simple/.
Firefox Marketplace provides details about the manifest file at https://developer.mozilla.org/docs/Apps/Manifest/, and it has a useful manifest validation tool at https://marketplace.firefox.com/developers/validator/. Robert Nyman’s talk “Web APIs and Apps” is a great primer for building apps for the Firefox Marketplace: http://www.slideshare.net/robnyman/web-apis-apps-mozilla-london/.
The latest version of the W3C widgets specification is at http://w3.org/TR/widgets/, and you’ll find a useful introduction on Peter-Paul Koch’s site—even though it was written a few years ago, and some small details of the spec have changed since then: http://quirksmode.org/blog/archives/2009/04/introduction_to.html.
The PhoneGap project is at http://phonegap.com/, and the API documentation is at http://docs.phonegap.com/. You can read the PhoneGap article “Beliefs, Goals, and Philosophy” at http://phonegap.com/2012/05/09/phonegap-beliefs-goals-and-philosophy/.
You can read more about the Titanium project at http://appcelerator.com/platform/.
Each smart TV platform has its own developer forum, but a good example for getting started is Samsung’s site at http://www.samsungdforum.com/.
The Opera TV Store is gaining some traction as a custom-made solution; learn more about it at http://business.opera.com/partners/tv/store/. The Dev.Opera site has some great reference articles on designing and developing for TV at http://dev.opera.com/tv/.
The Webinos project, which aims to create a standard common device API, is hosted at http://www.webinos.org/.
The Mozilla Developer Center has great AppCache documentation at https://developer.mozilla.org/en-US/docs/HTML/Using_the_application_cache/, and Mark Christian and Peter Lubbers created a handy page of AppCache facts at http://appcachefacts.info/. For all of AppCache’s drawbacks and tips and techniques for using it, read Jake Archibald’s “Application Cache is a Douchebag” at A List Apart: http://www.alistapart.com/articles/application-cache-is-a-douchebag/.