I love having widgets of all kinds on my iMac -- even things like the Ski Report (I live in Florida), ESPN (it's not football season), and Flight Tracker (I rarely fly). I even have similar ones (though Apple calls them webapps) on my iPod Touch. Since I've exhausted all the webapps for the touch that I'm interested in, I was glad to hear Widgetbox announced a gallery of widgets just for iPhone and the iPod touch users. Check it out via any browser, or right from your iPhone.
Now, most widgets are Flash-based, but these aren't and therefore don't use Apple's SDK, but they're cool and work well nevertheless. Among my favorites are the Yahoo! News RSS feeds, Random Quote Generator, and the Flickr slideshow.
While there's not a ton of widgets available just yet, there are around 32,000 developers in the Widgetbox community so I suspect the gallery will be populated pretty quickly. There's even a short video tutorial on how to make the iPhone widgets, in case you're curious -- or motivated.