jQTouch is a jQuery plugin for developing mobile web apps.
It takes an HTML page with several sections, and creates a view for each div. The main view is the div with id "#home".
Now that most recent browsers support HTML5's localStorage (a local key-value store), it's possible to have a settings page for a web app that doesn't require users to sign in: their settings are stored locally.
This data can be erased, though, if the user clears the temporary data stored by their browser - similar to cookies.
HTML5's client-side SQL databases allow data to be stored more permanently (until the databases are erased), but aren't yet supported by all browsers (Safari & Chrome, but not Firefox).
This example web app, using jQTouch in the client and PHP on the server, provides settings which are stored in a client-side database if available, or localStorage otherwise. Add a feed URL and it should be remembered next time you visit the app.