Another example of creating a mashup with RSSBus with just a little bit of code: FeedMapper.
Lots of services let you plot individual items on maps. Some even let you plot multiple items on maps. But I don't know of any that let you plot any feed (with georss data, that is) on a map. Taking advantage of feeds with georss data in them, FeedMapper will plot events contained within the feed on a Virtual Earth, Google Earth, or Yahoo map (Yahoo mapping only works in Firefox).
Update: Where's Tim lets you map feeds. Here's a Yahoo map where a feed of text messages sent to Tim is mapped. Here's the same map, where my Upcoming events dynamic feed is mapped (I set the location querystring to “Lawrence, KS“). Thanks Tim!
Technorati : api, atom, mashup, rss, rssbus, upcoming.org