Is there an emulator for Raspberry Pi that I could use to try to familiarise myself with the environment?
And in my case something that will work on OSX.
See this post re. using VirtualBox to run a virtualized version of Ubuntu. It comes configured with QEMU to emulate the ARM CPU and run Debian on ARM.
It doesn't provide any emulation of the Pi's hardware interfaces though, if that's what you're looking for, it just provides a virtualized copy of the OS.