Here's an example of the sort of thing that can be done with it. In the first picture, choosing to give the sky reasonable lighting ended up darkening the barn to the point where the image was delete-worthy. But Silver Efex Pro not only salvaged it, but created a dramatic image that I like a lot. Other than color removal, the only change was to the lighting.

All major paint manufacturers offer that on their sites. Go to SW for instance. Free is only so good at distinguishing the boundaries though.

Does anyone have any suggestions for free floor plan software? I just want to make a single simple 2D floor plan for a house that I rent out. It doesn't even need to show furniture, but I wouldn't mind if it did. I just want to show room location and sizes and I'd prefer not to have to draw it up on paper. :-) I'd be willing to pay about $10 if free isn't an option, but it needs to be really easy to use.

If you're looking for photo editing that has cut and paste capability, MS Paint will do it. You can draw or paint over any photo. With only a mouse or trackpad, you are pretty much limited to the line and shape tools for drawing. If you have touchscreen and stylus, you can use any of the painting and drawing tools.