DarkPlaces - Covered in second post
FitzQuake-SDL - Covered in third post
Here is a detailed description of how to compile Quake on a Mac. At first when I was playing around with OS X I found this a little frustrating:
This makes the assumption you aren't necessarily familiar with OS X and where stuff is and don't have XCode installed, Xcode being essentially the OS X equivalent of Visual Studio.
You can download Xcode from Apple.com (Use Google to find), but for OS X 10.5.2 had Xcode on DVD disk #2.
Going to use Fruitz of Dojo as the engine, the source and download is .
Installing + Setting Up XCode
1. Insert DVD #2; the follow comes up, double click the Xcode Tools folder:

2. Double-click XcodeTools.mpkg; run the installer to install Xcode.

3, You also need gcc 3.3 for the Fruitz of Dojo port. Insert DVD #2 again if needed and double click on the Packages folder.

4. Double click on gcc3.3.pkg to install gcc 3.3
Starting XCode
1. Click Finder (the little happy guy on the dock at the bottom left of your screen

2. Click Developer → Applications → then double click Xcode

3. Click File → Open and locate Quake1.xcodeproj which in Fruitz of Dojo is located in the Mac OS X subfolder of the Fruitz of Dojo source. (For example, if the Fruitz of Dojo folder is on the Desktop, this would /Users/YourUserName/Desktop/Fruitz of Dojo/Mac OS X/quake1.xcodeproj)
4. Now have this on the screen. Click Build and Go, which will build and run it.

5. The End
If you are trying to compile FitzQuake-sdl you will need to download some stuff from the SDL site. Assuming all goes well I'll quickly document that too for both FitzQuakeSDL and DarkPlaces.