When the stories about Roundup started floating around, I switched to 30% strength vinegar with a squirt of dish soap in it. It kills weeds and undesired plants off just as quickly and effectively as Roundup did, but obviously it does not prevent new seeds from sprouting. It is indiscriminate, whereas Roundup selectively targets broad-leafed plants, so you want to avoid getting it on grass. I use a big tarp to mask off the grass if I am using it heavily along the lawn borders. It's very effective for things like borders, gravel paths, stuff like that.

Also, instead of smelling like a chemical factory, your yard will smell like salad dressing for a day or so.