you could try and download the Hercules Emulator (Free) and the old IBM MVS mainframe operating system MVS 3.8J which has COBOL,Fortran,PL/1, Algol, IBM mainframe assembly language etc etc with it. It's quite fun running an old real main frame OS on your laptop.
The whole MVS system and Hercules emulator can be quickly and easily installed from the MVS TURNKEY CD. (Free again)
It runs fine on Linux --you'll need to install a 3270 emulator (usually always included in your Linux distro as C3270 or similar).
Here's a link
You'll also learn some interesting stuff about Mainframe programming as well.