So here is where I’m coming from. I’ve read the Quran twice, read some short books about Islam, but with the other thread that talked about this I started wondering if there is a way to understand the variations of Islam in terms Christians could relate to.
So those of you who can take a shot at this: To which varieties of Christianity would you say Sunni, Shiite, Wahhabi, etc. correspond the most closely?
I really don’t think you can do that sort of cross-mapping in anyway that doesn’t sow a lot of confusion.
Tamerlane is right, of course, that there’s no particular reason to expect a correspondence between, say, the Sunni-Shia split and some particular Christian split, because it was caused by specific historical circumstances. Even more broadly than that, there is no particular reason to think that since we put both Islam and Christianity in the category of religion that it follows that they both have the same general shape, any more than we expect Formula One, freestyle parkour, and NCCA basketball to roughly correspond because they are all sports. It is a common and misguided pastime to try to understand Islam through the lens of Christianity, but it often gets things very wrong (as in the case of those calling for an Islamic Reformation).
But, of course, the sects can be described “in terms Christians could relate to” without trying to analogize every sect to a Christian equivalent. It’s called “English” and is found (among other languages) on Wikipedia. Perhaps if OP has particular questions, he or she could start with those.
I would just like to commend you on this thoughtful, thorough, and concise answer. If we had a “Like” button, I’d have pushed it.
One could make a broad comparison between the Catholic/Orthodox split of 1054 to the Shia-Sunni split because both of them broadly involved questions over ultimate authority and jurisdiction. The comparison is, however, somewhat weak because the Catholic/Orthodox split was arguably simmering for a while and was largely complete, except in name, many years before the formal or official split of 1054. It is also different because the Catholic/Orthodox split involved an argument over whether or not there should be a single bishop with authority over the entire church (Catholics said yes, the Pope, Orthodox said no, the Pope is a fine bishop but he’s our friend and colleague, not our boss. Pointy hats and fancy robes ensue). The Shia/Sunni split, iirc, wasn’t over whether there should be a single Muslim leader (which was a given), but on who that leader should be.
Fuck that! Sunnis are Catholics, Shi’ites are Protestants, Alawites are Mormons! 
I don’t think I made my question clear. I was asking about in general, not me specifically. What I meant was that, for people who don’t want to or don’t have time to read the details, is there a way to explain to them quickly and in terms they can grasp.
Sunni are like Catholics in that they are considered the original core group from which the Shi’ites split, and, like the Catholic/Protestant schism, it was mainly about a question of organizational authority – in Islam’s case, the question of who should have been Mohammed’s successor as Caliph, Abu Bakr (Sunni) or Ali (Shi’a) – and, like the Catholic/Protestant schism, it also led to divergent developments of other aspects of doctrine. Alawites are like Mormons in that they’re just that different from the mainstream in their theology.
Got a cite for that? Why isn’t the other way round?
Yet the Shi’a have saints and the Sunni do not.
Because Mecca is Sunni territory, I suppose. Also, numbers, there were always more Sunni. Also, political hegemony; Sunnis held the Caliphate and Shi’ites didn’t.
See post #2.
So you don’t have a cite. I didn’t think so.
Well, if you want to be pedantic, there are more than a few Protestants who don’t consider the Catholics “the original core group” from which the Protestants split. In that, the Reformation created two new groups - one being referred to as Roman Catholic and the other as Protestant - and that pre-Reformation the church was the property of both groups.
(Personally I’m fine with saying that the Protestants split off from the Catholic tree, but some of my fellow Protestants get very mad when you say that - I have one Lutheran friend who is very adamant in saying “We didn’t leave; we were kicked out”)
Those discussing which is the “original” Christian church all seem to be forgetting the Orthodox branch of Christianity, which has at least equal claim to being the original branch with the Roman Catholics.
Western Christians have been forgetting about the Eastern Church since 1054, if not before :).
That’s because they split away!
There’s also Baptist Successionism (pretty much limited to Independent Baptists, I think). It’s the theory that Baptists, that is to say, Christians, never broke with the “Church” of Rome because they were never really part of it; when Constantine founded his fake “church,” the real Christians went underground and continued to practice real Christianity for centuries, until the Reformation when they re-emerged. I read about it one of Jack Chick’s comic books, though he did not give it that name.
And it is very easy to forget about it even after being reminded; I shall proceed to do so. Orthodox Christianity almost never seems to make any news any more.
Mecca is a common territory. It may be controlled by a Sunni state, Saudi Arabia, but the Shi’ites go on pilgrimage there as well, and they’re allowed to, too. It is Islam’s holiest site for both Shi’ites and Sunnis.
Also, the Shi’ites had their own Caliphate; it’s called the Fatimid Caliphate and it stretched on lands in modern day Algeria, Tunisia, Libya, Egypt, the Levant and Saudi Arabia, and it lasted for 160 years. Hell, the Fatimids built Cairo and al-Azhar University.