Believe it or not, this week was the first in 2013 that the Dow Jones Industrials (DJINDICES:^DJI) didn't manage to post a gain, as today's 49-point gain for the average left the Dow just shy of the 14,000 level, and down about 16 points on the week. Nevertheless, with the Dow having posted a nearly 900-point gain so far for the year, bullish investors can't really complain, especially as the aging bull market nears its four-year mark.

Among Dow stocks, Hewlett-Packard was the biggest gainer, but UnitedHealth Group (NYSE:UNH) climbed more than 1%, as well. Peer Molina Healthcare rose more than 10% on the day, as margin pressures on the company appear to be waning, which bodes well for players across the industry. But, increasingly, UnitedHealth's biggest prospects for growth are overseas, with its recent acquisition of a big stake in Brazil's Amil marking a huge opportunity for the top health insurer to diversify away from political threats in the U.S., and build itself up as a true global health-insurance powerhouse.

Elsewhere, Caesars Entertainment (NASDAQ:CZR) exploded 38% higher after reports that New Jersey Governor Chris Christie would allow a 10-year trial period for online gaming in an effort to bolster the health of Atlantic City's casinos. With Caesars being the biggest operator in the New Jersey market, it stands to gain the most, but Boyd Gaming (NYSE:BYD), and its Borgata casino could also benefit. Boyd jumped more than 9% on the day. Online gaming has been a long time coming, but if it takes off, it could truly revolutionize the entire gaming industry.

Finally, RadioShack (NYSE:RSHCQ) jumped 10%, after naming Joseph Magnacca as its CEO. Magnacca faces an uphill battle, as the electronics retailer's strategy to focus on smartphones and mobile-plan sales has run into the familiar roadblock of hurting short-term profits due to subsidies. The bigger concern is that much of Magnacca's experience comes from the drugstore industry, which is obviously much different from RadioShack's business.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter @DanCaplinger. The Motley Fool recommends UnitedHealth Group. The Motley Fool owns shares of RadioShack. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.