We have developed an open source, collaborative platform for researchers to develop, compare, and improve medical image registration algorithms. The platform handles data management, unit testing, and benchmarking of registration methods in a fully automatic fashion. In this paper we describe the platform and present the Continuous Registration Challenge. The challenge focuses on registration of lung CT and brain MR images and includes eight publicly available data sets. The platform is made available to the community as an open source project and can be used for organization of future challenges.