Obtaining Mainframe Experience w/o a Mainframe?

Nice2Cats asks: "So I'm reading all over about how companies are desperate for people who know how to work mainframes, especially now that IBM is shipping them with Linux. But how -- short of a course with Big Blue or some other exercise in expensive formal education -- can I acquire even the most basic information or experience with big iron? There doesn't seem to be many tutorials or introductions online; what would be nice, but I can't seem to find either, would be a simulator that would run on a PC. All I want to know is if I like enough to be seriously interested."