Leveraging redundant resources is a common means of addressing availability requirements, but it often implies redundant costs as well. At the same time, virtualization technologies promise cost reduction through resource consolidation. Virtualization and high-availability (HA) technologies can be combined to optimize availability while minimizing costs, but merging them properly introduces new challenges. This paper looks at how virtualization technologies and techniques can augment and amplify traditional HA approaches while avoiding potential pitfalls. Special attention is paid to applying HA configurations (such as active/active and active/passive) to virtualized environments, stretching virtual environments across physical machine boundaries, resource-sharing approaches, field experiences, and avoiding potential hazards.