There are a lot of maps out there showing what is going on in Iraq. Some are better than others and most tell only a part of the story. However, by combining the maps together one can gain a good understanding of the situation on the ground.
The Washington Post has a good map showing the ethnic breakdown of Iraq as well as the latest updates. Note how the Islamic State of Iraq and the Levant (ISIL, aka Islamic State of Iraq and Syria (ISIS), aka al Qaeda in Iraq (AQI)) has been temporally stopped at Samarra, the northern outpost of Shia Iraq. The remaining 100 miles to Baghdad will be much harder if not impossible for ISIL as they will be fighting on Shia Arab land against Iranian-trained local militias and not on Sunni Arab land against poorly motivated troops. Also note how the Kurds have advanced outside their Regional Government and into disputed Kirkuk. This will pose problems in the future as Baghdad will be unlikely to reassert control in Kurdish-annexed Kirkuk.
Long War Journal has a great map showing cities and towns in Iraq and Syria occupied by ISIL.
View Iraqi and Syrian Towns and Cities seized by the Islamic State of Iraq and the Sham in a larger map
This Washington Post map shows ISIL controlled areas as islands of population surrounded by desert connected by the only major roads in the hinterlands of Iraq and Syria. Although I do not think ISIL control is that solid, established in eastern and central Iraq as shown. (The West Bank is shown separate from Jordan but the text buffer covers most of the border)
While I do not like this map on Twitter showing ISIL control as a solid block, it does a good job showing how the group is focusing on controlling the oil wells and fields. ISIL likely is selling this oil on the black market thus making it a self-sufficient terrorist army.
This map by a Twitter user, Ghazi, is quite good. It explains areas of control versus areas of freedom of movement, and it shows how the post-World War I division between Syria and Iraq is basically over (for now at least).
Finally, though no longer novel it is always important to note geographic knowledge is power. Here is a photo via FlashPointIntel of an ISIL officer planning the offensive using Google Earth.