Why is English written and read from left-to-right as opposed to right-to-left, top-to-bottom, or (not even sure any language does this) bottom-to-top?

Whatever way one writes, there may be questions on that!!

Wikipedia says "Several scripts used in the Philippines and Indonesia, such as Hanunó'o, are traditionally written with lines moving away from the writer, from bottom to top, but are read horizontally left to right." Incredible! But it turns out Hanunó'o is usually written on bamboo sticks and the writing is done bottom-to-top (this answers one of Chris's questions as well); presumably they rotate the bamboo stick before reading.

Writing in English was derived from writing in Latin (it's mostly the same alphabet, after all), which in turn was derived from writing in Greek — which was written from left to right. So this is why all European writing systems go from left to right: because they're derived from Greek.

Many languages that existed before the invention of ink were written right to left since this is the more natural for right handed people to hold a chisel in the left hand and the hammer in the right. After ink became the main method of writing, writing from left to right became preferable since it avoided smudging the ink.

It is known that Chinese, Japanese and Korean are written in vertical columns going from top to bottom and ordered right to left because it "facilitated writing with a brush in the right hand while continually unrolling the sheet of paper or scroll with the left". (The Chinese invented paper, after all.)