Here are three sites to help you find the best deals:
Slickdeals: This community of savers is posting great deals year round, but their tenacity around the holidays is something to behold. At the time of writing this, nearly all the major big box stores' Black Friday ads are available in PDF format on Slickdeals - giving you an inside look at the best deals on eReaders, TVs and bed sheets. Search the forums for specific items you are hoping to nab - because another Slickdealer may have already found a great price.
CyberMonday: This site also offers year-round deals, but its real value is in their Twitter feed and email alerts. On November 26th, they'll be sending tweets and emails by the minute as new deals pop up online. The website also tracks coupon codes, so don't click "Buy" on anything until you've checked for additional discounts here.
BFAds: If you're wondering if a store will price match or if a deal you saw in the paper will also be online - this site is helpful. They keep track of retailers making changes or accommodations and post daily updates. They also get some of the ads of smaller, less busy Black Friday spots, such as JoAnn Fabrics and Bass Pro Shops.
(Images: Flickr user Kristina D.C. Hoeppnerlicensed for use under Creative Commons and sites listed)