Well, I just finished making my PBASIC emulator, RoboEmu(working title), usable. Please note that this is not anywhere near as functional as Matt's, and is still a very early alpha release of a very early version. Of particular note is the absence of gosubs, for-loops, and multiple program slots. It also has a few quircks with the comparison evaluator, mostly dealing with support of NOT and ~ since these operators are unary as opposed to all the others which are binary. Anyway, the GUI is semi-functional, so feel free to check it out.
If it throws an error, I'd greatly appreciate a copy of your code so I can debug all the little glitches. For now, it only runs under Windows, but porting to Linux (or any other OS) shouldn't be too hard as everything except the GUI and _itoa(MS specific, I think) are ANSI C. Once I finish the Windows version, I plan to do a quick port to gnome/gtk+. If there is interest in other OS's, let me know and I'll see what I can do.
As always, Source and Win32 executable available at
http://FIRSTprograms.tripod.com/Programs.htm. If you feel like it, take a look at RoboGUI while you're there. It's more-or-less the opposite of the PBASIC emulator. As always, I'm looking for comments, suggestions, and bugs.