In a History 101 course my professor mentioned that Washington wasn't technical the first president since there were 7 or 8 people who were president before the United States was established. Is this true? If so, who were these people and what would they be called if not "President of the United States"?
Washington was the first President elected under the present Constitution, which was enacted in 1789. For the first 13-odd years of the United States, the country was governed under the Articles of Confederation, which was a much looser union and lacked a "President" in the current sense of the office. The Articles did provide for a "President of the United States in Congress", but that position functioned more like the Speaker of the House or a majority leader, and was part and parcel of the Congress itself. Washington was the first person to hold the office of President as a separate branch of the government.
While the other comments on this thread are correct, it should be noted that Washington was still the first President of the United States. The President of the Continental Congress had a job more akin to the Speaker of the House or President of the Senate: a facilitator who ran meetings and managed debates. It was not a position with much by way of executive authority. Policies and administrative positions were determined by Congress, not the President.