NBC Washington, around 10:30 AM today, said that cell phone communications and Internet access could be adversely affected by a CME starting late today. That could include wireless Internet in general.
The official NOAA (Space Weather Prediction Center) forecast is for a moderate geomagnetic storm Sept 12 becoming strong Sept 13 because of the second larger coronal mass ejection, link here. There is a chart PDF that explains the terms. A "strong" storm could cause some voltage problems and spike false alarms (maybe in home security systems). It doesn't sound like Armageddon. Maybe electronics should be unplugged or well shielded by UPC's or only stronger surge protectors,
The European Space Agency has a blog posting suggesting that the strength of a CME will not be known until the flare passes a Lagrange Point near the Earth, about one hour before first impact. Get out your calculus and physics books; this sounds like a good free response question for an AP test.
CNN's Amanda Barnett makes a flippant comment "You might want to keep a flashlight handy" in her article Thursday, and I don't think that's funny.
Generally, power companies could make their big transformers more resistant to big CME's by building in excess capacity, over what customers use, to handle the overloads and short circuits created by CME magnetic field reversals. But in an area with heat waves, that's hard to do. The wrong-loop in the 2003 failure in the northeast, while manmade, is similar to what a CME could simulate.