Virtualization is a promising solution to develop complex embedded systems with real-time requirements. This paper discusses the current state-of-the-art in virtualization technologies, with a particular focus on solutions for embedded real-time systems. Several such solutions have been developed over the past decade, and in this paper we give an overview of the more well known technologies and we provide a comparative assessment of key virtualization techniques available in these solutions. Gaps and lacking pieces are identified and further development and research is suggested.