Don't look for just the mac version, though. They won't work on OS X without firing up the Classic environment. There are a bunch of different programs that will run the .DAT files for Macs, though. Zoom is the program I use.
Agreed. If you're new to this stuff:
The basic gist being that, lucky for us, Infocom made their games easy to port between systems by using a "virtual machine." Their games consist of a data file, universal to all operating systems; and an interpreter, particular to each operating system. Buy any version of Infocom games and as long as you can read the disk/CD, you can pull off the data files. Then you just use an interpreter specific to your platform (like Zoom for OS X, or WinFrotz for Windows) to play the game!
Thanks! I'll look into it. ^_^