I love my cast iron skillets. I have 5 of them. 2 fryers, 1-12 inch, 1-10 inch and 1-5 inch. I try to use them for as many things as possible.
* deep frying
* cake (very moist results)
* pizza (much better than the stoneware)
* frittata (the crust will be divine)
* shepherd's pie (or chicken pot pie)
* anytime I want to crust a piece of meat before putting it in the oven
* breakfast casserole (allows you to have a good crust on your bottom hash brown layer)
Cast iron takes a little bit longer to heat up than stainless steel (about 30 seconds longer), but it retains heat for many more minutes than stainlesl steel. That means you can turn your heat source off and your food will continue to cook for a while. This means saving gas or electricity depending on your stove type. You save of dish soap because you can't use it on cast iron. It can go from the stove top to the oven, you can put it on the grill, directly on a fire, and even on one of those homemade coffee can stoves! It is truly the most green and economical cookware I have found. Plus it is cheap!
How many cast iron skillets do you have and what do you use them for that's different?