After hearing so much about it for years, I've recently made time and read The Wealth of Nations. It's full of amazing insights that are still valid three centuries later. Thoughtful arguments in favor of free markets are balanced with lucid exposure of capitalism's limitations and inefficiencies. Overall, a thoroughly anti-dogmatic read, and a big improvement over 99% of subsequent economic writings.
If you can read German, I suggest perusing Silvio Gesell's "Die natürliche Wirtschaftsordnung". The author belongs to the rare-breed of free-market socialists, and has some interesting ideas about money and land.
