http://lulcards.com
Been working on this since January. RubyMotion experience was very positive, made development both enjoyable and I'd like to think faster. (Found a few bugs though!)
Running on AWS via OpsWorks. Using Amazon SWF for backend fulfillment workflows, which is amazing and not something I see mentioned often. Postcard printing/mailing by Amazingmail, payments by Stripe, address resolution by SmartyStreets (who are great and hooked me up with with free unlimited API calls for a year.)
Would love any feedback or suggestions, thanks!