McClatchy has an interesting piece on Iranian Brig. Gen. Qassem Suleimani, the head of the Revolutionary Guard's Quds Force. The story includes an awfully high percentage of anonymous sources, and the title might be a little hyperbolic, but I think the overall points made are fair enough.
Iran has a lot of sway in Iraq, which is normal. What's silly, though, is that Americans see this as some sort of meddling, because Iranian interests in Iraq are not always the same as American interests (although I'd argue that they coincide much more often than either side would like to admit). If Iran were occupying Mexico or Canada, you can be sure that the US would be "meddling" as well.
As for the actual article, I don't really have too much to add, except that it's important to look at Iranian involvement in Iraq not as a spoiler or as some diabolical force. If the US is going to come to terms with Middle Eastern players (of which Iran has become a major one, due in no small part to American intervention in Afghanistan and Iraq), Washington is going to have to look at Teheran (and Damascus and Hezbollah and Hamas, for that matter) as actors who have interests in the region that can't be run over roughshod by America.
This is a reality. So just as when one deals with Zimbabwe, it's necessary to take Pretoria into account, or how when dealing with Burma or North Korea one can't ignore Beijing, the road to peace in Iraq must necessarily pass through Teheran, but not in the way that American hawks would like it to.