I am an amateur Biblical scholar (emphasis on the "amateur"). I have been trying to learn Greek so I can read the New Testament in the original one day. (Any observations about being a shameless nerd are readily agreed with.) Many are surprised to learn that the oldest manuscripts of the New Testament were originally written in Greek (rather than Hebrew), and a number have asked me why. The reason is actually that Greek was the international language of the time. It was the language that people published in if they wanted to reach a wide audience, and that was the case with the early New Testament.
By contrast, the Old Testament really was written in Hebrew - or at least, most of it was. Scholars believe some of it may have originally been written in Aramaic - a Semitic language closely related to Hebrew. In the words of my church's Bible Dictionary: "The original language of most of the Old Testament is Hebrew, but a few portions ... were written in what is popularly called Chaldee, but more correctly Aramaic." (Source: Entry on Bible itself)
My church's edition of the Holy Bible
I don't have any plans to learn either Hebrew or Aramaic; as they are difficult languages for English speakers, and my primary Biblical interest is the New Testament; but I thought that as long as I had a copy of the New Testament in the original Greek, I might as well complement it with a copy of the Old Testament in the original as well. Thus, I looked into what version to get; and found that this was easier said than done.