There are a number of Web sites that'll show you Black Friday sales before the fliers hit your mailbox or the local paper.
Have you ever noticed that sometimes the best deals, are the least advertised? You can see where other shoppers are finding good deals on Web sites like slickdeals and fatwallet. Just check the hot deals forum on either site.
Now, if you want to wait for what you think is a good price for an online product, check dealalerter.com. You can compare prices and ask to be alerted if the product falls to the price you're willing to pay.
Also remember that whenever you see or hear the word "sale" don't just think it means you're automatically saving and getting a good deal. One of the keys to saving money is to really know what a good price is. You can check the price history of items on pricespider.com. Once you know the range, then you'll know if you're getting a good deal.
Most Web sites are updated daily during the holiday season with new sales and discounts.