As another Valentine's Day has come and gone, it's a good time to focus on relationships both past and present. As stock benchmarks go, the Dow Jones Industrials (^DJI -0.76%) are relatively faithful, making changes to the average's constituent list only infrequently. As we saw last September, though, Dow breakups do happen -- although in this case, things have turned out quite well for the stocks the Dow rejected, as Alcoa (AA), Hewlett-Packard (HPQ 0.56%), and Bank of America (BAC -0.59%) have all topped the Dow's 5% gain by a substantial margin.

For Alcoa, the secret to the aluminum giant's 38% gains since last September is its commitment to finding ways to go beyond simply selling aluminum as a commodity. In December, Alcoa signed a supply contract with Airbus, showing the huge potential that the aerospace industry has to provide demand not just for aluminum generally but for specially crafted aluminum products designed not just for light weight but also durability and functional design. Similarly, the redesign of Ford's (F 0.46%) F-150 pickup to use more aluminum will benefit Alcoa, which is one of Ford's top suppliers as the automaker aims to cut vehicle weights and improve fuel efficiency. By recasting itself as a high-margin specialty producer, Alcoa can recover even in a poor environment for raw aluminum prices generally.

Hewlett-Packard is up more than 42% since giving up its place in the Dow, as the former PC giant aims to find a new role in the tech industry. The company has made big strategic moves in recent months, with everything from selling 2,400 mobile patents to industry leader Qualcomm and unveiling an Android-driven desktop computer to entering the 3-D printing business and releasing a smartphone in India. These disparate strategies might smack of desperation, but they show the drive with which HP is looking to find a new, viable niche in a rapidly evolving tech world.

Bank of America is the laggard of the three rejected Dow stocks, but it's still up almost 16% since leaving the Dow. Huge buybacks of shares at an average price below $14 per share have proven prescient for the big bank, and strength in its consumer credit card division as well as its global wealth and investment management business has driven profits higher. The bank still has further to climb, as it still pays a minuscule dividend, and its return on equity is relatively low. But having defied the risk of failure during the financial crisis, Bank of America looks primed to keep rising as long as the industry holds up.

Look beyond the Dow
What these three stocks show is that being in the Dow isn't the end-all be-all of investing. Often, leaving the Dow seems to be a good incentive for companies to really start taking off, finding ways to reinvent themselves and prosper.