If you want to run Windows apps on your Mac, there are now a few ways to go about it. First there's Boot Camp, the official solution that will let you boot into an installed Windows partition. Then there are virtualization solutions like Parallels or VMWare, which "pretend" to be a separate hard drive with an installed Windows partition. Finally, there's emulation, and that's what CodeWeavers' CrossOver does. Rather than an actual Windows installation, CrossOver pretends to be Windows and allows Windows apps to run on a Mac, even without an actual Windows CD.
Impersonator is the company's code name for version 10 of the app, which was just recently released. CodeWeavers' Jon Parshall told me the most recent trends in emulation are away from standard apps like Office software and games, and into more niche apps like specific business and industrial software. CrossOver's compatibility list is better than ever, and the new version introduces a feature called CrossTie. CrossTie will both install CrossOver and get it up and running with a specific app directly from one file downloaded from CodeWeavers' website. For example, if you want to play Battlefield Vietnam with CrossOver, you can download the CrossTie file, follow some easy instructions to create a "bottle," hook it up to the game, and you're good to go.
I saw one run in action in the company's booth (while surrounded by celebrity impersonators -- the company was good at grabbing attention during the show). It seemed really simple to set up, though I didn't spend a lot of time checking out how it ran. CrossOver has 8200 apps listed for compatibility, and there are about four to five hundred CrossTie files available, with more coming all the time.