If I take the hard drive out of my macBook Pro and put it in a non-apple laptop, will it boot? I've just upgraded my (2011) macBook Pro to use an SSD. So I've now got an old hard drive laying around with OS X on it. 

I've also got an old HP laptop laying around.  If I put the drive in the laptop do I end up with a 'hackintosh', or will something crazy happen?
It won't boot, building a hackintosch machine takes more effort than just swapping a hdd.
Macs have a different bios than windows pc's and this is not stored on your hdd but in the machine itself.
Osx needs this special bios to run and "talk to" the components of your mac.
Also, osx might not have the drivers available for the components in your pc.

you could google for info to make a hackintosch