Stores typically have sales especially early in the morning on Friday. They are often very good deals. But getting up early and waiting on long lines isn't what I call fun. Monday there are also sales online for "Cyber Monday."
One of my local stores is opening at 3am for their "doorbuster" sales. That's the middle of the night. ToysRUs is opening at 10pm on Thansgiving and then again at 5am Friday.
Some stores also do price matching, even for Black Friday deals (Wal Mart has been advertising here that they will price match). That might be a good alternative if you have a store near you that will match prices.
newegg.com has started their deals already. They are real deals, but are limited and serve (1) to get some publicity when the TV and newspapers cover the lines and (2) act as loss leaders to get traffic into the stores.
In the olden days, say 15 to 20 years ago, the "sales" were because some goods were not moving. In theory, the Christmas sales season is from Oct 1 to Dec 24, so if its not moving by the Friday after Thanksgiving, it may not be going to sell.
But the term "black friday" was retailer short hand for the day that they finally turned a profit, into the black. Most retailers lose money most of the year and only make a profit during the Christmas period. The rest of the year, the retailer would be better off locking the doors, turning off the lights and laying off all the sales clerks.