The Sunni Side of the Street
According to the Sunnis, everyone but them are infidels. The Shi'ia feel the same way, but with the exception of Iran they aren't trying to murder everyone else. Hell, according to the Sunni leaders in Iraq, even Sunnis who vote are infidels!
This leads me to what really seem to be the only two solutions over there. Option 1 would be to let the Shi'ia and the Kurds round up all the Sunnis and put them in camps - just as the other arab nations did with the Palestinians. Every time a bombing or shooting takes place, remove some of those in the camps - permanently.
Of course, there's the second option. With the Kurds in the north and Shi'ia in the south, Option 2 would open up a lot of land in the center of the country. If you can't get along, get it on.
The nicest thing about Option 2 is that it would be strictly an internal national matter - just like Rwanda or Zimbabwe, so the U.N. wouldn't say boo about it. It would also get rid of the need to build all those camps in Option 1.
Of course, if you see a third option - or think I'm being overly harsh - I'm always open to convincing (but you'd better have a damn good argument!).