This year I tried winter sowing my tomatoes and I suspect I will have a bumper crop.
I took 2-liter plastic soda bottles, about 1/3 the way down I cut through the plastic, nearly all the way around but not quite (leaving a "hinge"), punched holes in the bottom, added potting soil, planted my seeds, sealed the incision back up with packing tape, watered well, and put the containers outside ... in February.
The seedlings know when it's time to sprout. I kept my winter-sown containers in a 2-flat arrangement -- a flat with holes nestled in a flat without holes. This allowed me to bottom-water them. It also allowed me to lift out the first flat (with holes) if it rained a lot and I needed to drain the containers.
Last weekend I planted them (most of them anyway ... I ended up with over 50 seedlings so will give the rest away), carefully removing each seedling from its soda bottle and transplanting as usual. No hardening off required, since they've lived their entire lives outdoors. The cold Spring temperatures have prevented any significant growth spurt so far, but once we have consistently warmer conditions I'm sure they'll take off.