If I recall correctly, nominal voltage in the US is listed as 120V +/- 10%. This accounts to normal swings in grid power. Note this is supply to your meter. After voltage drop on heavily loaded circuits to the end receptical, you could be looking at even lower.

We had a misbehaving power transformer feeding our house when we moved in. It took some convincing but the power company finally replaced it (and upsized it as it was near capacity anyway). I'd start with the power company and complain. It sounds like you've either got a high voltage condition, or perhaps frequent spikes.

As others have pointed out, you can install a line conditioner (essentially an active heavy duty transformer) which will stabilize the voltage, pulling up brownouts and pushing down spikes. These are often used in conjunction with a UPS, or as a combination unit. APC sells both types of units.