The process is actually dead simple.

1. Find a USB stick, an external USB DVD drive, and a Windows 7 install DVD.
2. Boot up into OS X.
3. Run the Boot Camp Assistant and transfer the Windows Support files to the USB stick.
4. Restart the computer, holding Command-R to boot into Rescue mode.
5. Select the computer's main partition (the largest one) and erase it (select MSDOS format).
6. Connect the external DVD drive and put in the Windows 7 install DVD.
7. Restart the computer, holding the Command button to boot from DVD.
8. Go through the Windows 7 install process.
9. Once you're logged into Windows, insert your USB stick. In the "WindowsSupport" folder, run "setup.exe" to install all the appropriate hardware drivers.

Done!

Now, if you're like me, and you neglected to do step 3 before wiping OS X, there is, fortunately, an alternative. I found a direct-download link on the Apple discussions site to the latest version of OS X Lion's Boot Camp files and extracted the WindowsSupport part on my Windows box:

1. Download OS X Lion's Boot Camp files
2. Open the pkg file with 7-Zip and traverse through the archive to Payload\Payload~\.\Library\Application Support\BootCamp\WindowsSupport.dmg\
3. Extract the file 0.Apple_ISO.
4. Rename it to something convenient, like support.iso
5. Open the ISO in WinRAR, then drag its contents onto your USB drive.

This took me a few attempts, since there are several direct-download links to different versions of the Boot Camp files... I needed the set that was right for my particular model.

To celebrate, I'm thinking of using this image as my desktop background.