Solaris Containers (otherwise known as Zones, although there is a minor distinction) are a slightly different type of virtualization, if you use a wide-ish generic term.

There's a very good Q&A on Consolidating Servers and Applications with Solaris Containers on the Sun Dialogue Programs page.

There are some limits to the Solaris Container (they are designed to provide multiple Solaris containers - there is no emulation of other operating systems, although a Linux container module is showing some promise), but for compartmentalizing multiple Solaris applications (and web application serving is a good example) they are a more efficient virtualization model than some other solutions.