How can I prevent weed seeds from sprouting next spring?

Well, its that time of year (for me at least) to start clearing the garden and preparing it for winter. Unfortunately, I just got a bit too busy this past season with life stuff, and the weeds got out of my control. I'm in the process of cutting/pulling out what I can, but some of them have even gone to seed. I'm afraid that this cycle of endless weeds and crabgrass will continue forever unless I do something.

What are my options for killing off weed seeds in the soil before they can cause trouble next year? Is there any sort of short-term herbicide I can put into the soil now to kill off the seeds, and would wear off by next spring? I thought about using Preen granules, but as far as I'm aware, that doesn't actually kill the seeds, it just keeps them from sprouting within the 3-month window, and so it wouldn't actually stop anything from sprouting next spring.

If herbicides aren't an option, what else can I try?