Here's an interesting graphic that shows the consequences of a massive solar EMP...
Starting in the center, you can see that power generation is hit the hardest. The transformers that the grid relies on are big, expensive...and not protected from EMP. It would take years, literally, to replace them. Scientific American had an article detailing the consequences and I talked about them here, but Business Week just posted an article about what would happen (the graphic's from that article) and basically, we're screwed.
If you rely on municipal water and waste treatment, you need to consider alternatives. My septic system has a pump because it has to regulate flow; the ground percs too well and the system has to slow things down so as not to overwhelm the drainfield, so in this worst case scenario, eventually the system will fill, and fail. Although this isn't something that will happen this week as far as anybody knows, preparedness involves thinking through the what-ifs like this.
Water's not so much a problem here in the PNW where I live, and I've got two large stainless pots and the makings of a Berkey knockoff from plans on the Web to filter rain water, and the parts to make a water collection system. But waste treatment...that's another kettle of...well, it's a problem.