I know for there's Fluid and Prism (there are others, that's the one I used to use) that let you load a website into what looks like a standalone app.
In Chrome, you can create desktop shortcuts for websites. (you do that from within Chrome, you can't/shouldn't package that with your app) Chrome Frame is different:
Google Chrome Frame is a plug-in designed for Internet Explorer based on the open-source Chromium project; it brings Google Chrome's open web technologies to Internet Explorer.
You'd need to have some sort of wrapper like that for your webapp, and then the rest is the web technologies you're used to. You can use HTML5 local storage to store data while the app is offline. I think you might even be able to work with SQLite.
I don't know how you would go about accessing OS specific features, though. What I described above has the same limitations as any "regular" website. Hopefully this gives you some sort of guidance on where to start.