Cast Iron is an old marvel that should never be abandoned. If you have cast iron pans and dutch ovens, you know what I mean. If you don't, I'm about to convince you to get some.
Cast iron is the original non-stick cookware. If treated well the pan remains stick-free and, instead of leaching toxic chemicals into your food as teflon has been known to do, it leaches iron into your food - a supplement that many of us, especially nursing mothers and vegans, need more of. Cast iron is also extremely cheap. I would suggest buying it new, unless you can find used pans (usually at yard sales and barn sales) that aren't completely caked with grease (though there is a method of cleaning these which is fairly easy). My favorite brand is Lodge Logic, which comes pre-seasoned and is a bit thinner than other brands. A new medium sized pan costs $12.00 and it will last you your whole life and then some - which is the other appeal of the stuff - it's indestructible. Don't order cast iron online. It's too heavy to be worth the shipping fee.
I would go ahead and buy a small pan (the perfect size for 2 eggs sunny-side up) and a medium pan (12 inches round is the perfect size for making lunch and dinner for 2-4 people). If you've gotten this far and want more, my next suggestion would be to buy a large pan (if you can lift it) for dinner for 6-10 people, a dutch oven (a deep-dish, lidded pot which is great for baking, stove-top cooking, simmering for long periods of time, and also useful for camping), and a griddle (a low-sided flat pan, either round or rectangular made for cooking pancakes and anything else that likes to be flipped a lot). You can also buy lids (which I wouldn't recommend as it encourages bad habits - see below), all sorts of intermediate sized pans, and pots too. I'd stay away from cast iron pots. They lend a bit or a metallic taste to things that need to simmer for a long time, and heavy-bottomed steel pots work just as well.
How to treat your cast iron
The basic technique for keeping your cast iron stick-free is to rinse it immediately after use with hot water (no soap!), scrub with an abrasive to get the bits out (some people say never to use steel wool, though I do) and then put it right back on a burner so that all the water in it boils off. Turn off the heat and immediately drop a bit of oil in (just enough to lightly coat the entire pan) and rub into the pan with a towel. I keep a special cast-iron-only rag on hand because you will never be able to wash black grease off of your nice towels (some people just use paper towels, I have also used brown paper bag bits).
If your pan or dutch oven smells, this is because you store it covered for too long, allowing smells to settle. From now on, store food in another container and, when not cooking, do not put a lid on your pan. Store your lid and dutch oven/pan separately. The way to de-funk cast iron is to preheat an oven to 300 degrees and, while it's heating up, rub salt into all of the internal surfaces of the pan. Don't be meager on the salt. When the oven is up to heat, put the cast iron in, close the door, and reduce the heat to 250. Let it sit for at least an hour. Then, while still hot, rinse it out with water. The water should evaporate off on its own, but if not, return to the oven to dry. The next thing you cook in the oven will be too salty which is why the first crepe was said to be "for the pan."
Once your pan is adequately seasoned, you should only have to season it properly with oil once or twice a week, unless you're cooking something acidic (such as tomatoes), which will strip the seasoning. Washing your pan with soap strips the layer of grease that keeps the pan non-stick. Don't do it.
Like all things old and long-used, cast iron is incredibly forgiving. If something goes wrong, all you need to do is to salt the pot, heat it in the oven (if it's really bad, go at it at 200 degrees in an oven for 4-6 hours), however, things probably won't go wrong, and if you occasionally wash it with soap, it'll be fine - just be better about seasoning it with oil that week.
In case you need another reason to go for cast iron, all real cornbread is made in cast iron pans.