Read background info at : http://www.sajalkayan.com/complete-asynchronous-ad-loading-using-dfp-and-labjs.html

Usage:-

Following variables need to be prepopulated.

1) DFPpubid = "ca-XXXXXX" - where XXXXXX is your adsense publisher id as seen on top right corner of adsense pages
2) adslots = An array with adobjects for ad locations

`
var DFPpubid = "ca-XXXXXX";
var adslots = [{"pubid": "ca-pub-XXXXXX", // pubid again
  "slotname": "test_async_lb", // ad unit name from DFP
  "width": 728, // width of ad unit
  "height": 90, // height of ad unit
  "target": "leaderboard" // id of the <div> to be populated with the ad
  }, // repeat for as many ad units needed
  {"pubid": "ca-pub-XXXXXX",
  "slotname": "test_async_sky",
  "width": 160,
  "height": 600,
  "target": "skyscraper"
  }];
`

After the above 2 variables are populated, include the script using LABjs

    $LAB.script("dfp-lab-iframe.js").wait(function(){
      DFPasync(adslots, DFPpubid);
    })


Warnings:-
1) Requires LABjs to be loaded - http://labjs.com/
2) Uses DFP's iframe method, so no expandable ads - http://www.google.com/support/dfp_sb/bin/answer.py?hl=en&answer=90777
3) This is a hack. If DFP changes their ad loading mechanisms this may break your site.
4) I don't confirm or deny if this script voilates any TOS.
5) Goto 1)

document.write is evil. It must die!