Laws of Computing, Version 2.0 by CH Ting [pdf]

If you like Forth, you should also try doing programming "by hand" in PostScript. Unix dc is another fun stack-oriented piece of software where you have operand operand operator -- that is, postfix like an RPN calculator. dc is great when you have a bunch of numbers to add, because you can review things even after you've finished the computation. (Of course, a spreadsheet is even better.)