If you live above Zone 5 and the ground isn't frozen yet, there's probably a frozen crust by now, and you'll have to break that to make holes for your bulbs. I've done it, and it always means bloody knuckles by the time you're done, but it's worth it. I never saw the late-planted bulbs do any less in spring than the earlier planted ones. Like all things bulb, the Netherlands Flower Bulb Centre is the expert source for information on planting times. Here's their list of "last planting dates" by region:
As you can see, places like The Gulf Coast and California have plenty of time left. On the gulf, you can plant until mid-December, and in California, on through New Year's. (For the entire story from the NFBC, click here: Late Planting Dates for Bulbs and Wildflower Seeds. ) Here's the list of dates they recommend:
Northeast and Rocky Mountains, can plant bulbs until ground freezes Midwest, Appalachians, Mid-Atlantic Coast, and Plains States, plant through November 30 Pacific Northwest Coast, plant through December The South, plant now through December 15 Gulf Coast, plant now through December 31 California Coast, plant now into January.
So if you still have time and want to create a big bloom for spring, get out your shovel.