corn gluten meal is a working 'pre-emergent' form of weed control - it actually prevents the wee seeds from germinating.

but otherwise, I've found that the weed-block that works best... is two layers of courogated cardboard, or newspaper by the section (about ten layers. with the new soy-based inks, newsprint is a viable garden material again)

the basic technique is to soak the paper, and apply it to damp ground - I've successfully applied it OVER the weeds, and smothered even crabgrass. you then mulch over the paper. you can do this to the whole area, and then punch holes to plant, or you can plant, then paper over it.

it lasts one season, the worms LOVE you for it, it works as an effective method of water retention, you get a karma point for recycling all that newspaper (it took me two ream-sized boxes of other people's papers to do my back yard, which is likely smaller than your living room) and the scary thing is how well it works - so far, trumpet vine is the only thing I've found strong enough to 'break through'...and that particular volunteer is the bane of my existance.