WINE

WINE Is Not an Emulator.

It’s an application loader and a set of runtimes that allow you to run COFF Windows binaries in Linux (or other Intel-based UNIX variants, but with lesser success), without performing any CPU emulation.

What it “emulates” is the runtime environment for Windows applications by mapping Windows system calls to its own. So, no, it’s definetly not a mere emulator.

There ara a couple of useful pre-packaged WINE runtimes for the Mac that make it trivial to run some applications without the overhead of a virtual machine:

• Bottles, a modern front-end
• Wineskin, which creates neat packages with everything you need, including a minimal self-contained X11 runtime (and is therefore more likely to work with Lion)
• Winebottler, my old favorite.
• PlayOnMac, which is heavily oriented towards gaming.