It may be too late for carrots, but lettuces and spinach still have time to get a start. I planted most of my winter garden back in July and August. Brussels Sprouts, sprouting broccoli, kale, chard, chinese cabbage, winterkeeper beets, and spinach and lettuce (already harvesting from those).

If you want it to overwinter, it has to get big enough to establish before frosts. That means planting by around July 15, though maybe a larger transplant would make it. Otherwise it would have to mature fast before frosts hit, or be grown under some protection possibly. I've grown most from silver creek's list and also turnips if left in the ground will make great greens and flower buds in early spring.

As already suggested, it's too late for most stuff now, (but the time is perfect for garlic/shallots). I think most NW gardeners don't have enough good garden space to grow all the summer crops they want and still allow enough space for a winter planting in July too! So, by the time the summer crops are done, it's too late for winter crops.

But rather than leaving your garden soil bare, why not use a cover crop to grow over the winter and add nutrients for your spring plantings. Additionally, a cover crop makes for easier tilling come spring time - you just till the green cover into the ground and plant. Some even use fava beans as a cover crop, where you just may get a picking of young beans in spring just before you turn the plants under.

Cover crop seed is usually available from your local feed store or Grange.
jm

Come to think of it, Corn Salad may still do well. I have it self-sowing in my garden and I don't think much of it is growing yet. I don't do a good job of harvesting it though, as the leaves are rather small.