WebDock has been running a highly capable Linux version (60k transactions/min) in a plant since 2000. It works with Allen Bradley Ethernet PLC 5s and SLCs. I haven't had a chance to try it, so I'd appreciate, and will update this post with, feedback. Be warned, of course, that you get no promises, support, etc. That said, awesome! Maybe someone will put the project on Slashdot and get it moving!