Ha! TANSTAAFL! I love it! (though I doubt anyone else besides maybe Rod knows enough Sci Fi to get the reference)
Don't be so sure about that.
Oh, and besides the two that Mike recommended, I'd suggest The Moon is A Harsh Mistress and Time Enough For Love to anyone looking for a good Heinlein read.
Add
Glory Road to that list, a personal fave (Hienlen, extra pulp variety).
And I'll re-recommend
Stranger... If you only read one, this is it. Warning: I reread it a couple years ago, and Heinlen's 50's sensiblility and the chauvanism that was the norm is somewhat off-putting. Also, it's not as mind-blowing at nearly 50 as it was when I was 17 -- go figure.