Taking advantage of dual card slots on DSLRs

I have a camera here with two memory card slots. I have a little guy right here, and I am going to put a second one in. Now, we tend to see this more on expensive DSLRs, at least for the time being. This might be something that migrates down as time goes on. What I can do is, when I take pictures I can write it to the one memory card slot, and then I can take my favorites, and I can put it on the second memory card slot. It's really like having an external hard drive for your computer, but it's built right into your camera.