Indianapolis Motor Speedway spokesman Doug Boles said Monday's attack will be a part of future meetings to review what precautions should be taken at the auto race.
"I guess this will bring a new topic or dialogue to those discussions, to see if there's anything more we need to do to prepare with respect to what's happened in Boston," Boles said. "And we will learn more about that over the next couple of days, as the folks in Boston do, and we will be prepared for that."
At the Kentucky Derby, which pulls in crowds approaching 250,000 each year at Churchill Downs Racetrack, security was beefed up recently following the death of Osama bin Ladin.
"We are always in close contact at this time of year with the dozens of federal, state and local law enforcement and public safety partners who work with us every year on safety and security concerns for our major events," Churchill Downs spokesman John Asher wrote in an email. "We will be in close and frequent contact with them and rely heavily on their expertise, as we always do, in the hours and days to come."
In Boston, Bruins President Cam Neely, a former player, said the hockey game's postponement was made after consulting city, state and league officials. He said authorities are still gathering information and "it is vital they have all resources available for their investigation."
Fans arriving early for the Bruins' game were met by police who were in the area to secure the arena and a nearby federal building. One officer outside the players' parking lot was telling arriving spectators, "The game is canceled. We need you to exit the city safely and quickly."
Moments later, Bruins captain Zdeno Chara drove out of the lot, and not long after that the Senators' team bus left down a side ramp.
Police were searching all bags and people entering the train station below the Bruins' arena.
An electronic sign, which usually lists departure times, instead read: "We ask all passengers to be as vigilant as possible and alert authorities if anything suspicious."
The Red Sox game had been over for about an hour when the explosions could be heard at Fenway Park, about a mile from where the bombs went off at the finish line.
Major League Baseball called the bombings a "horrible occurrence" and said the league is monitoring the situation.
"The safety of everyone that comes to our ballparks is always our top priority and we will continue to do everything to ensure a safe environment for our fans," MLB spokesman Pat Courtney said.
President Barack Obama's news conference Monday evening was shown on the video board during batting practice before the Cincinnati Reds hosted the Philadelphia Phillies. There was a moment of silence for the Boston victims at that ballpark and at other major league stadiums with games Monday.