Once you've dragged them to the folder/s of your choice then just select them by clicking on them in iPhoto and press the delete key (which is located above the return key).
This will send them to the iPhoto trash which you will need to empty if you want to delete them from the iPhoto library.
Don't take this the wrong way, but why use iPhoto at all then? The whole idea of iPhoto is organize your photos. There are better free editors, and I don't you need iPhoto just to move images from a camera. The key to iPhoto is the use of keywords and smart albums. These will give you much more control over organizing your photos than a folder based system, plus give you a lot of other benefits as well.
Now, there is a view feature on iPhoto to just view the photo's . So put all your pics in the folders then make your default view All photo's. Then if a folder is not selected, then it will not show any photo's. That is what I am gathering you wish to do right?
Just make a folder on your mac and kill the 500mb install of iphoto.
Of course the default for iPhoto is to open when you attach a camera - thus people feel obliged to use it when they don't want too. I can't remember how to turn it off. I had to search for it somewhere.