  In the last few years, contributions of the general public in scientific
projects has increased due to the advancement of communication and computing
technologies. Internet played an important role in connecting scientists and
volunteers who are interested in participating in their scientific projects.
However, despite potential benefits, only a limited number of crowdsourcing
based large-scale science (citizen science) projects have been deployed due to
the complexity involved in setting them up and running them. In this paper, we
present CitizenGrid - an online middleware platform which addresses security
and deployment complexity issues by making use of cloud computing and
virtualisation technologies. CitizenGrid incentivises scientists to make their
small-to-medium scale applications available as citizen science projects by: 1)
providing a directory of projects through a web-based portal that makes
applications easy to discover; 2) providing flexibility to participate in,
monitor, and control multiple citizen science projects from a common interface;
3) supporting diverse categories of citizen science projects. The paper
describes the design, development and evaluation of CitizenGrid and its use
cases.
