Enter Parallels Desktop for Mac (originally Workstation for Mac), a true virtualizer. This allows users to run Windows within, well, a window on your Mac desktop. Parallels, unlike Boot Camp, can run just about any operating system you'd like, from MS-DOS to any flavor of Windows, Linux or Sun's Solaris, at the very same time as you run your Mac apps. (.)

Parallels missing a few pieces (3-D graphics, for one), has proven to be a little less compatible in some ways (support is lacking for some USB peripherals, for example), and is not quite as fast as Boot Camp. This speed issue is partly a result of the fact that the Parallels microkernel that sits on top of the physical Mac has to divide, allocate and direct resources between the Mac and Windows apps. But for those needing to run Windows and Mac apps side by side, Parallels is a real breath of fresh air.

Parallels recently announced the version of its next Desktop software, and it's available for purchase. Recently, the stalwart of the virtualization world, VMware, released the beta of a virtualization product for Macs called Fusion. (Read our of VMware Fusion.) And now the game gets really interesting.

VMware has some capabilities that top those of the Parallels product, particularly support for dual-processor virtual machines and support for 64-bit operating systems, both of which are due to be included in the next major revision of Parallels Desktop for Mac later this year. For its part, Parallels has some innovative features of its own, such as the Coherence interface, which allows PC apps to run directly on a Mac desktop.

Since competition drives innovation, it's likely that the virtualization options for Macs will keep getting better and better.