Answer:
There are about 40,000 different Christian denominations, almost every day there's another. Its not even something that can be counted and kept track of. However they can be roughly split into five major "families":
1: The Catholic Church
2: Orthodox Churches
3: "Mainline" Protestant and Anglican Churches
4: Evangelical churches and movements
5: Pentecostal churches and movements
There are others that do not quite fit into any of these 'families', such as the Church of Jesus Christ of Latter Day Saints (Mormons) and the Watch Tower Bible and Tract Society (Jehova's Witnesses). This is by no means to lessen them, it is simply a statement that they are very unique; and don't have as much common ground with any other group. However almost all of the vast number of denominations would fall under the category of Evangelical protestant, many of which are almost completely identical to each other. So there are a limitless number of denominations, however there aren't so many different churches in reality. And don't forget the more powerful Native American form of Christianity.
over 35,000 who all disagree with each other on at least one thing.