Look into the subject "lasagna gardening" in the gardening forum. I have recently discovered this process and have been using it to create new garden beds over my existing lawn. So far so good, but it has been only a few months.

Basically, the method tells you to put lots of layers of news paper or cardboard down first then some layers of manure, compost, organic materials etc.

I read somewhere when researching the subject on the web, that one landscape designer creates new beds by spreading cardboard/newspaper over the area and then covers it with 6" or so of steers manure and lets it sit over the winter...having a fertile weed-free bed ready to plant the following spring. The cardboard/newpaper layer kills the existing weeds/lawn underneath, but slowly composts away over time.

I would think this will work even if you have already removed the sod. It should supress any weeds lingering in the topsoil.

Bellagoss