I wrote about airport delays before, in which I've had a list of the 3 busiest airports in the US (Atlanta, Chicago, L.A.). Turns out, these are not the worst airports.
A recent Wired article rates 32 airports from good (Oakland?) to worst (Newark) based on average delay times, and your chance of being delayed coming to or leaving the airport.
I was a bit surprised reading that list (not surprised about EWR - I always felt it was a crappy airport), but LAX gets quite a good mark, and the order of crappiness changed a bit (LAX 5th, ATL 22nd, ORD 31st).
Wired also has a PDF file to summarize the list.