This blog entry (via Instapundit) explains why Islamists are not fascists.

The reason it's inappropriate to describe Islamists as fascists is simple: They're not statists. To Muslims, including that subset of Muslims I call Islamists (see below), a state is at best a temporary thing, performing certain administrative, organizational, or ideological tasks. It has no independent significance, as it does in, say, the Christian tradition. ("Render unto Caesar" and all that.) Islamists aren't trying to create a state in which all the parts work as one; their ultimate goal is a stateless world in which everyone worships Allah.