Is It Possible to Install OS X on an External Drive for Use with Any Mac? My dad would like to encourage me to learn how to program in C++, but he doesn't want anything that could possibly go wrong with any of the computers that we own while I am doing so to affect any of the data associated with their other user accounts.  As such, he would like to give me an external drive for me to use as an isolated programming environment.  This would be relatively straightforward to set up, but I was wondering if I could install OS X on this drive in such a way that I could boot it no matter which one of my family's computers it was hooked up to so that I could use whichever one is available as they become so.  Is it possible to do this at least for a late 2007 aluminum iMac and a 15-inch MacBook Pro that my dad bought late in the summer of 2011?
Yes it is quite easy.

For example, my MAC had a bottle of Champagne poured on it (long story, short) and I removed the hard drive and placed it in another machine. I also later took that drive and placed in an external enclosure and booted from it by using the "OPTION" key when booting. This brings up a list of all accessible drives INCLUDING NETWORKED DRIVES if accessible.  So you could configure your DEVELOPMENT drive on your network and boot from it HOWEVER unless you have GIGABIT network it would be slow. 

So to create an external bootable self contained OSX drive I recommend the following tutorial, BE ADVISED it will clear off any data on the external drive and your doing all of this at your own risk.

http://support.apple.com/kb/ht5911