Eight legs? Must be a spider although it does not seem to look quite like a spider. These creatures with small bodies and eight legs are commonly known as harvestmen although I have no idea why other than they are most commonly found in August, harvest time. Although they are not spiders they are related but they are very different as they have an undivided body, whereas spiders have a thorax and abdomen. Harvestmen have just one compartment for all their bits!
This particular species does no have a common name, just Phalangium opilio.
They are mainly nocturnal but you do see them by day, usually resting. What I find even more incredible is that they feed on other small animals, both living and dead. They may not look much but they are obviously ferocious little creatures. They are venomless and quite harmless to us of course.