Just ask yourself, "Who lives here?" Who do you think the party would bump into travelling through the area. It doesn't have to be especially memorable, it's just something to break up the monotony of travel.
When I moved to Texas, we passed a LIVE FISH truck like 5 times. To this day, that's the only thing we remember about that trip.
My standard are farmers and hunters, but nothing messes with a party more than telling them they see a possible foe that doesn't want to fight.
A dragon passing overhead, or a drow that notices the party, then vanishes into the forest. A long-beard wizard that ports in, looks around confused, hrrumphs, then ports out again.
I especially like to use either overpowering and underpowered foes for this, so a low level party would see the above, but a mid level party may stumble across a goblin that runs away when he sees the party approaching or a displacer beast that abandons a kill.
Not everything out there is as bloodthirsty as PCs.