I've been playing with a writable Web application called NumSum, a Web-based spreadsheet. Here's a little test spreadsheet I created. They have a "blog this" feature which creates an iFrame of the spreadsheet. Here's what it looks like:

Go ahead and change some cells and it will recalculate. Your changes won't be persistent. This is unlikely to put Office out of business anytime soon, but as a demo application, it shows just how far this might go. Doesn't feel like a Web-app, does it?

NumSum was built to show off the capabilities of TrimPath, a "web Model-View-Controller framework that gives you Rails without the Ruby." Heck, just a good set of JavaScript templates would make my life easier right now.

Apparently, someone has taken the TrimPath SQL parser and the AJAX massive Storage System to build a JavaScript database, one more piece in the microapplications puzzle. With an offline datastore, you can do things that require only occasional connectivity.

Tip of the hat to Tim Shadel for pointing these out to me.