Cloud Computing is a promising paradigm designed to harness the power of networks of computers and communications in a more cost effective way. Clouds provide elastic capacity to serve a wide and constantly expanding range of information processing needs, including government, military, business and education. The Cloud Computing paradigm is maturing rapidly and is being considered for adoption in government and business platforms. Open source systems refer to software systems whose source code is available, allowing for immediate incorporation of improvements and adaptations of the system by its users. This paper reports on an evaluation of open source development tools for Cloud Computing. The main tools examined are Eucalyptus, Apache Hadoop, and the Django-Python stack. These tools were used at different layers in the construction of a notional application for managing weather data. The results of our experience are reported in terms of a capability matrix that grades nine different aspects associated with the use of these tools in the development and deployment of applications in open source Cloud Computing environments.