You might think from glancing at stories in the press that the gay and lesbian population in America isn't making much progress in its struggle for acceptance. The number of states permitting gay marriage isn't skyrocketing. The White House isn't advocating equal rights. Episcopalians and other churches are divided regarding gay clergy.

But look behind recent headlines and you'll see signs of progress -- often involving the corporate world, and therefore the stock market. According to a recent Gallup poll, 89% of Americans support equal job opportunities for gays, and 54% believe homosexuality is an acceptable alternative lifestyle. These numbers have been rising over the past decades, and the business world has taken notice.

According to a recent Human Rights Campaign report, 253 of the firms in Fortune 500 (that's 51% -- a new majority) now offer health coverage to the domestic partners of gay and lesbian employees. That's up from . um, one, when Levi Strauss did so way back in 1992. That's not so long ago, folks, and that's quite a lot of progress for 14 years. Additionally, 430 of the 500 companies have policies banning discrimination on the basis of sexual orientation, which is a 46% increase in the past five years.

Interestingly, the firms offering domestic partner benefits aren't just the usual suspects. Sure, Apple Computer does so, and so does California-based Charles Schwab. But also making the list are firms some might describe as not-so-progressive or particularly left-leaning, such as Clear Channel Communications, which added the coverage in 2006. Also joining the club in 2006 were 3M, Automatic Data Processing, Duke Energy, Ecolab, Harrah's Entertainment, Lowe's, and SUPERVALU.

Does this mean that these firms are leaning to the left now? Should conservative investors be worried? Not necessarily. Some firms might be doing what they deem is the right thing to do, but others might simply be doing what's good for business. Inclusive policies such as these can attract and retain more employees and can also reflect favorably on the firms in the public eye.

If you care about how socially responsible the companies you invest in are, learn more about socially responsible investing with these articles:

You might also opt to let some smart money managers find and invest in them for you -- via socially responsible mutual funds. Shannon Zimmerman recommended one in our Champion Funds newsletter service a little more than a year ago, and it's up some 13%, vs. 7% for its corresponding index.

Charles Schwab is a Motley Fool Stock Advisor pick. 3M is a Motley Fool Inside Value pick. Duke Energy is a Motley Fool Income Investor pick. Take the newsletter that best fits your investing style for a 30-day free spin.

Longtime Fool contributor Selena Maranjian does not own shares of any companies mentioned in this article.