A bunch of people have emailed me about getting Hypercard stacks running under emulation.
Here is a pretty easy guide to running a Hypercard stack on a recent Mac (eg. running Mavericks, Mountain Lion, etc):
Place the Hypercard stack you want to access somewhere within your user folder: eg. Documents, or Desktop.
Download this zip file [95mb] containing the SheepShaver classic Mac emulator bundled with Mac OS 9 and Hypercard.
Extract and open
hypercard.sheepvm. This should boot Mac OS 9.
On the Mac OS 9 desktop there should be a disk called "Unix". This is a virtual disk which actually lets you access files on your computer (eg. outside the emulator). Opening it is equivalent to opening your OS X