Although the term was originally associated with theologically conservative Protestant groups, over time fundamentalism has come to refer to any religious group (usually conservative) that rigidly adheres to a set of beliefs, which is why it is not unusual to here people write or speak about Islamic fundamentalism, Jewish fundamentalism, Hindu fundamentalism, and so on.
Not all fundamentalists are conservative, however. One of the more humorous varieties are those whom I call liturgical fundamentalists, who are often quite liberal on theological issues but are quite legalistic when it comes to following the lectionary or displaying liturgical colors. I know clergy who possess a low Christology (i.e., Jesus may have only been a human not God incarnate) and don't take the Bible literally (or too seriously, for that matter), but heaven forbid you show up during Advent wearing a red stole (Hint: Red is for Holy Week -- see the chart above). I'm preaching on St. Paddy's day, and I hope people don't get too upset when I show up wearing a green stole (Hint: I should be wearing purple -- see the chart above).