Can anyone point me to a good, easy tutorial on programming for XFree86?
by XFree86, I'm guessing you mean GUI programming. You basically have two options, GTK++ and QT. Do a seach on google for either one of those and I'm sure you'll find something. good luck.
You could start looking around here (A great UNIX related site)
check out the X11 toolkit section 'cause I don't think you want to use xlib or xt (they're very low level).