Virtualization on Apple Hardware
Possibilities to allow multiple OSes to run at the same time:
- VirtualBox - currently free.
- VMWare Fusion - currently CS has a license for teaching.
- Parallels - as of 2013 that seemed the fastest (on MacOSX 10.8 and 10.9); it costs about $50 per machine.
If you only need the option of multiple OSes at boottime, then BootCamp can do that.