Don't panic or spend a ton of money!
Getting rid of carpenter ants is cheap and easy.
Just get some ant poison cups, and put them in the path. Takes about 36 hours, but they die.
Then leave more bait traps out, as more tend to come after periods of rainy days.
Also, spend a little time around the outside of your house, if you're patient and walk slow, you'll find the trail that is eventually entering your house somewhere. If you impatient, you can sprinke diazanon or some other ant powder around the foundation where they're crawling up, then leave an antcup closer to their nest.
I used to think they came into your house due to moisture problems, rotting beams, etc... but this is not true!
I had an old house, and assumed rotting sill or wet walls were attracting them, but have owned 2 new houses since, and they were coming in the first year the houses were built. They will make a nest anywhere they find hollow areas, like under vinyl siding, but their "master" nest is outside somewhere, as others have said. Ants will gravitate to rotting sill or other wood for making a nest, but don't need it necessarily. If you're near a woodsy area, they will come in no matter what. They're just exploring for food.
The thing is, more keep coming. Don't lose patience, just put out more poison.