Based upon a mean earth radius of 3,959 miles, a black hole with an event horizon the size of earth would require a mass of 1080 suns.
If we were REALLY lucky, we might have noticed the gravitic lensing of the stars in night sky, but the odds of that with such a small black hole are very low.
This would be equivalent to a star 1080 times the mass of the sun mucking about with the gravity while interacting with our solar system. Let's assume it affects our orbit once the gravitic pull on us is stronger than that of the sun. The gravity equation (f=Gm1m2/d^2) tells us that if we multiply m1 by 1080 then d must increase by root(1080)=33 AU to keep f constant. That's just outside the orbit of Neptune. So if it hits us from the side, we might witness the loss of Pluto as a planet for the second time in our lives... :)
I'm going to assume that the black hole isn't moving at an extreme speed relative to our own solar system, and that it comes at us perpendicular to our orbital plane.
While the sun wouldn't suddenly wink out - the event horizon is too small for that - its gasses would be rapidly siphoned off to its new stellar neighbor. 921
The sun is the largest object in our solar system by far, so the force of gravity between it and the black hole is strongest. This is probably the first clear evidence we would have of anything being amiss - sudden warping and offgassing of the Sun.
As these gasses are accelerated toward the event horizon, they would heat up and combust, just like they do on the sun itself. Now we would see major surge in high energy particles like xrays and gamma rays coming from within our neighborhood. Look up pulsars for more info.
Assuming the radiation doesn't strip us of the ionosphere and fry the earth completely, we would be pulled out of orbit by the much heavier black hole. Even if we managed to miss falling into the black hole itself - very likely considering it's relatively small size - we'd probably grab enough momentum to say sayanora to our annual orbit. We'd either follow Haley's comet and start taking trips out to the kuiper belt, or we'd be slingshotted entirely out of the solar system. Either way, say goodbye to the sun!
We'd more than likely die from starvation and darkness rather than earthquakes and event horizons. 99