It seems like you can't turn around these days without seeing a billboard or hearing a commercial touting some big corporation's latest green initiative.

Nestlé is getting into the fair-trade coffee business with its new Nescafé Partners Blend brand of instant coffee. BP boasts about its commitment to renewable energy with the new slogan "Beyond Petroleum." Even Wal-Mart, which has been criticized for its ethically suspect labor practices, is trying to go green. The company recently invited former Vice President Al Gore to speak about global warming and has pledged to bring organic food to the masses.

Is corporate America truly discovering the joys of environmentalism and social responsibility or is this just greenwashing?

It's probably a bit of both, but many environmentalists are genuinely impressed by the efforts large corporations are making to go green.

"I think it's an extraordinarily exciting time," says Joel Makower, founder of Greenbiz.com, an online resource center for businesses interested in becoming more environmentally responsible. "It's just in the last couple of years that we've seen a growing number of companies—from major banks to retailers to major industrial companies like GE, Dupont, Dow and BP—really begin to make significant commitments to sustainability."

So what does it mean to be a green company? Even the experts agree it's a moving target. "I've been in this for 20 years and I don't have a good definition," says Makower. "It's all a journey, not a destination. Companies are on various parts of the path to making themselves sustainable."

For a small company, going green might mean using recycled paper products, installing solar panels and using organically grown materials. For a large company, it might mean investing millions of dollars in renewable energy research, slashing carbon dioxide emissions and drastically reducing energy consumption.

What's considered green is continuing to evolve. "People are opening up to the idea that green doesn't just mean environmental anymore," says Todd Larsen, managing director of Co-op America, a national organization that works to create economic solutions for social and environmental problems. "It means environmental and social justice together."

Whatever the efforts are, companies are increasingly learning that green initiatives are not just good P.R., they're good business. "They're not just doing this to try to save the planet," Makower says. "They're seeing the huge economic potential. Instead of simply growing the bottom line by reducing costs, they're growing the top line by increasing revenue. This is creating new products and new markets and in some cases new companies."

Still, Makower says consumers have to greet green initiatives with a critical eye. "You certainly have to accept more than vague general claims like ‘We're environmentally friendly' and ‘We care about the planet.' You have to ask for details. If something is being advertised as a green cleaner, you have to ask, ‘Compared to what? What doesn't it have? Who says it's green?' "

When possible, Makower says, consumers should seek third-party verification of green claims. Fortunately, a growing number of environmental and social justice organizations are making it easier for consumers to see through platitudes and find companies that are truly committed to green principles.

Co-op America has a Web-based Green Business Pages, where consumers can search for everything from local architects who specialize in green design to clothing companies that use organic materials and environmentally sensitive production practices. To be included in the green pages, companies must meet strict standards and back up their claims with hard evidence. Nearly 3,000 companies have won Co-Op America's stamp of approval, including Patagonia, Aveda and Stonyfield Farm.

"We're looking at what kind of steps they take to green their processes and minimize their impact on the environment," says Todd Larsen, managing director of Co-op America. "We ask what processes are in place to conserve energy, minimize the impact on the environment, minimize the release of toxins."

GreenSeal is another non-profit organization that promotes the manufacturing, purchase and use of environmentally responsible products and services through a certification program. The organization works with manufacturers and government agencies to "green" the production and purchasing chain and certifies products only after rigorous testing and evaluation, including on-site plant visits.

Many communities have local organizations that support green businesses and help consumers evaluate them. In the seven-county San Francisco Bay Area, for example, local environmental organizations, utilities and government agencies have formed the Bay Area Green Business Program. The 10-year-old partnership assists, recognizes and promotes businesses and government agencies that choose to operate in a more environmentally responsible way. Its Web site offers county-by-county listings of businesses that meet the program's standards for conserving resources, preventing pollution, and minimizing waste. Similar programs have sprung up in Sacramento, San Diego and Monterey.

"We actually go on site and verify that the businesses have implemented measures that will conserve energy, conserve water and prevent pollution," says Ceil Scandone, regional coordinator for the Bay Area Green Business Program. "For us verification is key. They have to show they are doing something."