"Merchants can store their own products to our fulfillment centers and then, using a simple web service interface, fulfill orders for the products. That’s right – make a web service call, ship a product to a customer!"

"Scrobbler is a [ruby library] wrapper for the audioscrobbler (last.fm) web services." It looks very ncie.

Y!DN Weather forecasts by location, through API. I'm trying the "Weather forecasts" challenge in Rubyquiz (flexing muscles, etcetera) and it seems ilke a good place to start.