I've tried Fusion, Parallels and VirtualBox, but after Parallels wanted another $50 to upgrade from 4 to 5, I thought I'd go back to VB for another go. As I'm not a heavy user either (one or two apps), I installed Windows 7 and am now typing this to you from Chrome! Shared folders, networking and hard drive management are very easy - I'd definitely suggest giving it a go before dropping any dollars on the commercial products, especially if you're not after a specific feature of the big two.

I've tried both VMWare and VirtualBox. Unity alone may be worth the price if you use several Windows applications regularly - it lets you run hosted applications without the hassle of having to load the virtualizer, load a VM, and then fiddle about in a window each time. VirtualBox is free and works, but has a slightly awkward interface and little desktop integration.

@papercrane :
Unity feature: Run Windows applications like Mac applications, quickly switching between Mac and Windows applications, minimizing Windows applications to your Dock, and even store Windows applications in your Dock to launch at a moment’s notice.
http://www.vmware.com/products/fusion/features.html

What is the Unity feature, and how important is it?

I've been running Ubuntu on it for a while now, and I have no complaints.

To compare with VMWare, VB doesn't have the Unity feature, but that only works with virtual machines running Windows, so if you're running a free OS, run it on a free virtualizer!

Sweet. I didn't want to shell out for VMWare or Parallels since I just need to run Win 98 & WordPerfect 8 (from 1997) occasionally to open some old files & use my scanner (Xerox Documate 510, with no Mac or SANE drivers available). It works great for both -- USB support with the scanner is flawless so far. The only issue is that display options for Win98 are pretty limited but for something I use only a few times a week it's fine.

this cannot be universal since its a x86 virtualizer.

homepage says: "VirtualBox for OS X Hosts (Beta 2; Intel Macs only)"

i'm running a vista vm and an xp vm, and it is just as fast as fusion/parallels, and best of all it's free.

there is no coherence/unity equivalent, but other than that, i haven't noticed any discernable differences between the commercial software and this wonderful free offering.

I've installed OpenSuse using this. It was headache free.

I spoke too soon. VirtualBox does indeed feature automatic mouse capture, as well as seamless folder sharing. No drag and drop from the finder, but moving files back and fourth is generally not too difficult. This software works fine!