Entire living room circuit suddenly controlled by hallway lightswitch

Do you have any split-switched-outlets, where one outlet is switched and the other is not, but they are both in the same receptacle?

What you are describing SHOULD NOT BE ABLE TO HAPPEN if the wiring hasn't changed. If you have connected things against their product labeling, or used high current equipment (usually for prolonged periods of time), or if the wiring was done poorly, weird things can/will happen. One of those things could be risk of fire so it is best you just turn the breaker off in question until it is checked.

I would at least unplug everything, and use a basic incandescent lamp and check all outlets (each one individually), and write down which ones work, and which ones don't with the switch ON and OFF, and breaker ON and OFF.

If you aren't handy with a meter or are concerned to work with the wiring just call an electrician. They will appreciate your troubleshooting you've done and will almost certainly recheck it themselves. When all is said and done, you'll have peace of mind.