stack based languages

Hello, i am interested in learning a stack oriented language, so i started learning Forth. (from http://www.amresearch.com/starting_forth/)
Some alternatives i heard of are cat and factor.

What is best to learn from those? And suggest a good tutorial

FORTH:

: NEXT-FIBS OVER + SWAP ;
: FIB 0 1 0 2SWAP DO NEXT-FIBS LOOP DROP ;

I have to say I like Lua better though:

function fib(x)
  local a,b = 0,1
  for i = 1,x do
    a,b = b,a+b
  end
  return b
end