VitalSource is hoping to be to books what iTunes is to music: a place to browse and buy content. They back it up with an interesting client; it lets you annotate, highlight, search, and build cross-book outlines.
Apparently their backend applications have been running Rails for a while. But they’ve recently released their client software, and it runs Rails as well. Except… you won’t see it running in a conventional browser.
More details and a screenshot over at Dave Thomas’ blog. I find this fascinating, because on the one hand I love the ease of use that Rails provides the programmer, but on the other hand I still think that given the right task native desktop applications can provide a richer and more consistent experience for the user. While I long for a framework that makes straight-up desktop applications as easy as Rails makes pure web applications, amalgamations such as this are an intriguing compromise.