Over the course of its 38 years, Earth Day has evolved from a daylong awareness-raising event with limited appeal into a near universal campaign that reflects our increasingly eco-conscious times. For many years, business and industry, including supermarkets, ignored Earth Day because it didn’t represent anything of much importance — either to them or to their customers.

Boy, has that changed. Retailers today have sophisticated promotions marking the occasion. And many — the best, in our opinion — are thinking outside the 24-hour timeframe, calling attention to ongoing sustainable initiatives or perhaps using the day to kick off a new campaign.

There are a lot of creative retailer promotions out there that are kicking off tomorrow. Here are a few of the trends we’re seeing:

Bags, bags, bags: Offering reusable totes has become the most effective way for retailers to spread their green message. As such, stores like Tesco’s Fresh & Easy will promote them further by giving away their reusable bags for free. Others, like Bashas’, will give away totes to consumers who bring in their plastic bags to recycle. And some, like Whole Foods, are planning even bigger things. As has been widely reported, the Austin, Texas retailer will discontinue plastic bag usage starting tomorrow.

Come together: A number of retailers will also participate in programs organized by nonprofits or trade organizations. Kroger, Supervalu, Publix and others will join the Organic Trade Association’s Go Organic! promotion, which includes discounts and specials on organic goods throughout stores. In England, supermarket chains like Tesco and Marks and Spencer are participating in a promotion to raise enough money to offset one million tons of carbon by 2012.

Green Deals: Throughout this month, Wal-Mart is offering discounts on its many of its sustainable products. The Bentonville retailer is also offering new green items, like T-shirts made from recycled plastic bottles and bags of recyclable rubber mulch. Then there’s Schnuck Markets, which plans to unveil a “Green Cleaning” section in stores, headlined by brands like Seventh Generation and Clorox GreenWorks.

So, what’s going on in your store?