Thank you for the pointers on how to do this in Paint.net. Seeming like a bit much, I've opted to use Serif PhotoPlus 6 for my slicing and dicing needs and it seems to work pretty well. I now prepare my images in Paint.net, or otherwise, and then open them in PhotoPlus to cut them up.
Hopefully some gifted soul will develop a plugin to accomplish this functionality in Paint.net.
Take care,
Greg