Well is your power dropping out or simply "changing"? If it's an undervoltage situation, you would obviously see your electrical dim and maybe go out. An overvoltage situation wouldn't really be too noticeable in your home.You would see a spike as your power tries to return to normal after a dip or "brown-out". It's rare, but if it's bad enough it could blow your light bulbs out sometimes.
You may be able to get a quality UPS that switches over in any instance where your power isn't between 105-125VAC. This should help if you're having slight dips and spikes.
But, if you're just experiencing wide ranging dips and spikes, I'd suggest you get your electric co. out to inspect a few things. Dips/spikes like that may indicate a transformer issue or a poor neutral somewhere. Either way, it could be a serious problem.
Or your power company has been having a rough summer. lol