This week, Amazon announced Subscribe with Amazon. The offering is a subscription service for sellers of digital products and services. Through a series of APIs, subscription sellers can use Amazon infrastructure to offer products and services on monthly, quarterly, and yearly basis.
With Lemonade Stand, users can search for things to buy in a location-based manner, or add their own listings of things they wish to sell. The application is currently available as a client for Android, with a possible Windows Phone 7 version on the way soon as well, from a 3rd party developer that released an early version. Its Lemonade Stand API allows other developers to either code their own clients or use it in mashups.