What program is best to run windows on my mac?

Depends on what you're doing. Boot Camp will always have the best performance.

 

Like Tallest Skil said, it depends.

Here's a brief rundown:
Do you need native performance? Do you have XP SP2, XP SP3, or Vista? Then Boot Camp is for you.
Do you need to run versions of Windows Boot Camp doesn't support? Would you prefer not to have to reboot to switch operating systems? Then either Parallels Desktop or VMWare Fusion is for you.
Do you need to run just a few Windows programs, and would rather not use a full copy of Windows? Then, CrossOver is for you - if the programs you need work. Many do work in CrossOver, but there are also plenty that don't. If you're going to explore this option I highly recommend getting the free demo and testing the Windows programs you use to see if they behave properly.

 

You should MRoogle it. There are a lot of threads about this.

Here is also a good place to start.

 

wrldwzrd89 has the right idea; there are multiple solutions out there depending on what you want to be able to do, and the best way to decide which is right for your situation is to do a little experimenting with trial versions.

The Parallels Desktop 4.0 for Mac trial is here, along with the features:
http://www.parallels.com/products/desktop/features/

The trial has all the features and functionality of the full version, just with a 15 day time limit. After install, you'll be given the option to back up your data just in case you decide not to get a full-version serial key.

A big part of Desktop for Mac that gives you an advantage are the features and tools you're able to utilize while running virtualization software. It also comes with data backup and anti-virus software (Arcronis TrueImage & Parallels Internet Security - powered by Kaspersky) to use with your guest OS partition.

 

There is also the option of Crossover, to run windows based programs on a Mac without having to have windows.

 

There is also VirtualBox which is free and very nice but it has less support for OpenGL I believe.

Darwine can do a far bit as well, but also lacking in OpenGL support the last time I checked it out.

 

Parallels 4 is superb, virtualbox is free.

Crossover and Darwine are really the same thing, wine 1.1x - wine has excellent openGL support, DX8 is good, and DX9 is pretty okay.

It depends on what you want to do. Bootcamp offers the best experience, because you're just booting into Windows. Parallels, VMware fusion, virtualbox and Q-emu all offer virtual windows install with varying degrees of performance. And wine isn't windows, it lets you run a good deal of windows programs and games on the mac by providing the necessary windows sub-components to run them.

 

I use a combination of BootCamp and Fusion. I boot my Windows partition with Fusion when I'm just using Office or something lightweight that I need Windows for. I reboot into Windows natively mainly for games.

 

Between bootcamp and parallels, Bootcamp is ONLY running windows or OSX at a time, not both. So resources are not gobbled up. Parallel, both are running at the same time, o more ram is needed, as well as vid memory.