It's an Eastern Milk Snake. They are harmless and non-venomous.

You correctly ID'd the one at the top of the photo as an Eastern Garter(Thamnophis sirtalis sirtalis). The dark one at the bottom of the photo is a young Black Rat Snake(Pantherophis obsoletta). Black Rats don't hatch out black; they enter the world as a silvery-gray snake with a bold pattern of black blotches and lines, and gradually turn darker with each skin shed. This snake is still fairly young, as you can still see its blotched pattern visible, like the spots on a black leopard. Where you live, adult Black Rats usually are jet black with white undersides and throats, although in many places throughout their range, they will keep at least some visible dorsal pattern throughout their lives. I'm guessing that with different species coming into the basement, species with very different feeding habits, they are preparing to hibernate there. Both of these snakes are harmless, and will leave come spring. The presence of the Black Rats could be a deterrent for rodents to enter your home during winter.

It looks like one of the several tree vipers in SE Asia of the genus Trimeresurus. I am not familiar with the differnt species and subspecies. It could be a color variant of T. wagleri (Wagler's Pit Viper or Temple Viper).

Yeah, kidhorn2, WHY? Is it THAT difficult to simply learn something about snakes, and how to ID them? Seriously, I've taught second graders to do that, and we have quite a few venomous species in the Southeast where I live. You aren't exactly making yourself out to seem very intelligent by that statement. Explain to me this logic: if you know for a fact that dogs kill an average of 30 people per year in the US and send another 3 MILLION to the hospital, whereas snakes kill less than 5 people on average per year, why does it make more sense to hate snakes and not dogs? I can look at a snake and tell right away if it's venomous, and therefore potentially dangerous, but even a lifetime growing up around dogs and breeding dogs has not allowed me to be able to glance at a random dog and determine if that dog will bite or attack. I have far more reason to be concerned about a dog, than a snake. Even with a venomous snake, I have tools that allow me to safely pick it up and relocate it. It's easier, believe me, to pick up a large rattler than an angry 30-pound dog, and I've done both.