Snowfire with a little customistion (rotating images, width toggle removal) combined with a bunch of other Joomla add-ons (Community Builder, JoomlaBoard, Thyme, ZoomGallery) all work really well together. We're starting to get members adding content and lots of repeat visits and nice comments from users and well as viewers.
Built the weather component myself (my first Joomla add-on!). It draws images etc. from Ireland's Metrological service website and as such is only applicable to our wet & windy island!
well, I can't take all the credit. If you check out
www.met.ie
you'll see where I got the idea and a good deal of the code. All I did was adapt that and wrap it in a component. You expand, it would need to become a little more complex and I doubt if it would be possible to get weather data in a consistent format from various nationla weather services!
It does work well as a component though, doesn't it. The original idea is a good one with three day outlook configurable by parameters. A good idea, cleanly executed. It also works very well in the context of an outdoor organisation website (the idea to run the site as a sort of group communications hub - I'd like all members to have this set as their homepage and consult the weatheer chart when running events etc.)