Friday after Thanksgiving marked 2011's Black Friday sales. Retailers including Apple offered modest discounts on Apple products that day. Cyber Monday is the online extension of that sale into the following week.
13.3" 2.4GHz MacBook Pro ($1199): -$150 at Best Buy, -$149 at Amazon
15.4" 2.2GHz MacBook Pro ($1799): -$200 at Best Buy
15.4" 2.4GHz MacBook Pro ($2199): -$140 at MacMall, -$140 at Amazon
17" 2.4GHz MacBook Pro ($2499): -$150 at MacMall
Amazon's pricing is the most volatile and may change hour to hour. Best Buy's and MacMall's sale prices should hold throughout Monday.
Several of the vendors listed are affiliate partners with MacRumors and referred sales may benefit the site financially.