Terro.
Had a few ants creepin' into the house, from under the trim on a wall that backs to the garage. I was liek, WTF mates?
Laid out a couple of the Terro bait traps, within 60 minutes there was an assembly line of ants running from the trap, under the trim board, through the wall (wall backs to the garage), into the garage, and down into a crack at the corner. So now I know where thier base is.
The ants were like OMGWTFTERRO = TEH YUM.
1 day later, the ants = teh DEAD.
End result = no more random ants.
Yes, Terro = da bomb yo.
On a serious note, I highly recommend Terro baits. I previously also had a carpenter ant problem. I called Terminex, they were useless. Their stuff is basically the same crap you can get at the stores, and they just know where ants are "likely" to turn up.
Terro bait traps plus the Terro dust stuff (which you use to create a perimeter around the outside of the house) totally eliminated the carpenter ant problem.
Terro baits alone eliminated my recent problem (which were the smaller "house" ants).
I can't speak highly enough of this crap. It really works. You may need to spread around the traps to get the ants to do a feeding frenzy on it, but once they carry it back to the nest, all of them die.