Firebase, Parse

http://www.quora.com/Firebase/How-does-Firebase-differ-from-Parse#

Both Parse and Firebase allow for building server-less apps. 

Firebase is a real-time cloud data service. It is designed for building real-time, collaborative applications. Data in Firebase is standard JSON, and developers can access it using a client library or the REST API. When accessed through a client library, changes to data are synchronized in real-time to clients within milliseconds. Firebase provides a highly flexible expression-based security API that allows fine-grained control over data access by clients. 

Parse is a complete technology stack for building mobile apps. It provides a REST data api, push notifications, a Cloud Code JavaScript runtime environment, and social services. Parse has a variety of SDKs for all major mobile platforms as well as a Javascript SDK. Parse provides an access-control-list based security API, which it augments with its Cloud Code service to control data access by clients.