I've considered doing some shows on the mainframe. So far I haven't because I'm leery of using work assets for non work reasons. I would need to do that.

However, I do have a show in the works on my favorite editor, The Hybrid Editor, XE which works like the standard mainframe(ISPF) editor.

Might also do a show on the mainframe emulator, Hercules.

There are related topics I could do without using work resources, 
though. Rexx and COBOL come to mind.

But it's not likely I'll do a show on my day to day work on the mainframe.