quick question- how would you mitigate any exposure to pc-related viruses? what i mean is, if my main computer is say a Mac Pro, running Mac OSX natively, would my hard drive be more compromised and exposed from running windows via boot camp rather than virtually via VMWare or parallels?
my thinking is that running windows inside a virtual "box" would keep any viruses related to "pc" only inside that virtual system, thereby still keeping my physical mac osx native hard drive intact. does that sound right or am i missing something?
You are correct. Parallels and VMware both offer a variety of security settings that separate your Windows VM from your OS X host. At the most lenient, your OS X home folder is mapped transparently to your Windows home folder (so, for example, anything on your OS X desktop will appear on your Windows desktop; when you open your Windows 'My Documents' folder, it will show your OS X 'Documents' folder, etc

at its most secure, the only possible 'crossover' between OS X and Windows is if you share over the network.
VMWare's current version can run fully hardware accelerated 3D, even on the Windows desktop (so you get the shiny "Aero" desktop

and Parallels next version is slated to do so as well. It's not perfect, as many 3D apps don't work right, but for many, you take a negligible hit. (5-10%.) And both let you specify more than one CPU core to run in the VM. So if you have an 8-core Mac Pro, you could specify that your VM sees 4 cores. (Technically, OS X can still co-opt the CPUs, but for the most part, you will get full speed to Windows out of those CPUs.)
To be yet one more voice answering the original question: No, it is not possible to run two OSes simultaneously on "bare metal" hardware without the assistance of virtualization software. The closest you can get is to run a "bare metal" VM software, where the 'base' OS is just virtualization software, like VMWare's ESX Server or Microsoft's Hyper-V. The best of these even let you 'map' certain hardware devices to pass directly through to a VM, so that the hardware is accessed directly by the 'virtualized' OS. But these are meant more for server purposes, I don't know how well they would do with more 'workstation' uses. (For example, I don't know wether or not you could use two video cards, having each one assigned directly to each of your two OSes.) Parallels Server supports this "bare metal" mode, but that is $1300 all by itself, and only supports OS X Server, not OS X 'desktop', so you'd need to shell out another $500 for Snow Leopard Server.