[The following chart is a very rough equivalency between groups in the Islamic world and groups in the Christian world; it is for comparing social/historical parallels, not theological points. Persons somewhat familiar with Christianity but unfamiliar with Islam may find it helpful. People unfamiliar with either Christianity or Islam will only be further bumfuzzled.] Update (Sept. 30, 2011): An excellent & far more detailed & scholarly Primer On Islam may be found here.
Update (Oct. 1, 2011): At the suggestion of a reader, I have substituted the "=" symbol with "><" to indicate "more or less similar to" instead of "equals"
Shi’ite >< Protestant. Muslims who broke off on their own when they thought the Sunnis weren’t hard core enough. There has been a lot of friction & conflict between Sunnis and Shi’ites, but not all internal problems in the Islamic world originate there: The Mesopotamians (Iraqis) and Persians (Iranians) were at odds with one another long before Mohammed was born, just as The Troubles in Northern Ireland began long before Martin Luther cooked up Protestantism.
Taliban >< Ku Klux Klan. Most 21st century Americans don’t realize the Klan openly fielded candidates & occasionally won offices in the 1920s, and that in many Southern & Midwestern communities of that era thru the 1960s all public offices were held by Klan members or sympathizers. Like the Klan, the Taliban are sadistic bigots who cherry pick verses to justify their sadistic bigotry.
Al-Qaeda >< The Irish Republican Army. The IRA was a predominantly Roman Catholic gang of political terrorists seeking to overthrow English control of Northern Ireland and re-unify it with the Republic of Ireland. They did this despite Ireland & England agreeing to a 1919 peace treaty that gave control of Northern Ireland to England. The IRA waged a campaign of bombings and assassinations for decades before finally being ground down to submission in 2005.