Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Expect a flat start to the stock market today, as the Dow Jones Industrial Average (^DJI 0.40%) is set to rise by 17 points at the opening bell. Still, stocks are on pace for their best annual performance since 2003, with the Dow sitting on a 23% gain headed into the last days of the year. Meanwhile, news is breaking this morning on several stocks that could see heavy trading in the session, including CarMax (KMX 0.54%), Walgreen (WBA 0.57%), and Red Hat (RHT).

CarMax said today that third-quarter sales were up 13%, to $2.94 billion, and profit improved by 15% to reach $0.47 a share. The car retailer's comparable-store sales leaped higher by 10%, thanks in part to what it called an "attractive consumer credit environment." Still, CarMax's results were pinched by an uptick in cancellations of its extended service plans. The company also saw its third-party credit providers tighten their financing offers toward the end of the quarter, which could make it harder to keep car sales growing at a double-digit pace into next year. The stock is down 5% in premarket trading.

Walgreen this morning announced earnings results for its fiscal first quarter in which profit rose by 24%, to $0.72 per share. Revenue ticked higher by 5.9% to reach a record $18.3 billion as the company continued to gain market share in its prescription business. However, profitability took a hit as fewer new generic drugs entered the market and Walgreen ramped up promotions. Looking ahead, the company said next quarter should bring similar pressure from the relative lack of new generic drugs, and it will face a tough comparison with last year's winter quarter, which was the heaviest flu season in 15 years. Walgreen's stock is down 0.79% in premarket trading.

Finally, software company Red Hat reported surprisingly strong third-quarter earnings results. Sales jumped by 15% to almost $400 million as its enterprise Linux and JBoss Middleware products met with strong demand. Notably, Red Hat saw business pick up in Europe and among its U.S. federal government clients. Profit rose faster than revenue in the quarter, as customers embraced its cloud-based subscription products. After underperforming for most of 2013, Red Hat's stock is up 14.5% in premarket trading, at roughly the price where it began the year.