Marking its 41st anniversary on Friday, April 22, 2011 is Earth Day, which will be celebrated once again by millions around the world. A day that honors the planet and all living things that inhabit it, Earth Day traces its roots to the 1960s, and the first such event – then called an “environmental teach-in” – was held on April 22, 1970. Who would have thought that a grassroots effort to inspire awareness of the environment in the United States could mushroom into a global phenomenon celebrated in more than 175 countries each year?

If you’re an eco-minded traveler, you’ll be happy to know that a wealth of green hotels are at your disposal, most with programs in place that promote sustainable practices including water conservation and the use of high-quality, environmentally-friendly products. Better yet, select properties have earned LEED (Leadership in Energy and Environmental Design) certification, which attests that a hotel’s location and design meet high standards for environmentally responsible, sustainable development.

Go GREEN and read on for a sampling of eco-friendly hotels that prove style, comfort and concern for the environment can go hand in hand.

Seaport Hotel Boston: Seaport Hotel Boston offers Seaport Saves, a groundbreaking environmental program devoted to integrating conservation and sustainability practices into all hotel operations. If you happen to arrive in hybrid or electric vehicle, you can take advantage of a complimentary charging station – the first of its kind to be available at a Boston hotel – and a complimentary night of valet parking through the end of 2011. Other green hotel achievements include the installation of an ozone laundry system and the purchase of enough renewable energy credits to offset the electricity used to power all 428 guest rooms, guest floors and elevators for the entire year. With a yearly recycle rate of 43 percent, it’s little wonder the Seaport received a 4 out of 5 rating from the Green Key Eco-Rating Program.

The Orchard Garden Hotel in San Francisco

Kimpton Hotels: Kimpton gives a whole new name to eco-friendly luxury. It is the first hotel company to be 100% Green Seal Certified, and every one of its 140 hotels – from 70 Park Avenue Hotel New York to The Onyx Hotel in downtown Boston – has adopted environmentally friendly products and services. As part of its Earthcare program, Kimpton’s towel and linen reuse policy helps dramatically reduce energy use, as do energy efficient lighting fixtures and air conditioners installed throughout the hotels. Interestingly, Kimpton was also the first boutique hotel group to feature in-room recycling bins. Want a bite to eat? Head to any Kimpton restaurant and you’ll quickly notice menu options that might seem out of the ordinary, but are no less appetizing – from sustainable seafood to in-house purified water and organic tea.

The Orchard Garden Hotel San Francisco: Setting the standard for green hotels in San Francisco is this green boutique hotel near the city’s Financial district and just steps from Union Square. The Orchard Garden Hotel uses energy-efficient lighting, nontoxic paints, and Forest Stewardship Council-certified wood. In keeping with the eco-friendly theme, all guestrooms invite relaxation with soothing colors and fabrics in natural wood tones. This San Francisco hotel takes pride in being the first hotel in California, the third hotel in the U.S.,  and just the fourth in the entire world to be granted LEED certification. When the hunger starts to kick in, mosey over to the on-site Roots Restaurant, which offers locally sourced organic and sustainable foods.

Millennium Knickerbocker Hotel Chicago: Determined to lead the way in the adoption of sustainable practices at Chicago hotels, Millennium Knickerbocker Hotel Chicago has already implemented several eco-friendly measures aimed at conserving water and electricity. Among these are equipping rooms with water saving showerheads, toilets and faucets; installing energy-saving programmable thermostats; and ensuring that all equipment purchased is EnergyStar compliant. This Chicago luxury hotel at the gateway to the Magnificent Mile has also introduced recycling programs and eliminated the use of non-biodegradable Styrofoam cups and aerosols.

ARIA Resort & Casino at CityCenter Las Vegas: In a city noted for its lights and glamour, hotels are quickly going green in style, and this 61-story resort is certainly no exception. With a spa, 16 restaurants, 150,000 square feet of gaming, and 10 bars and restaurants, the property feels like a world of its own. ARIA Resort & Casino received LEED Gold Certification from the U.S. Green Building Council; it has also earned the highest level of recognition, 5 Green Keys, from the Green Key Eco-Rating Program, thanks largely to its water conservation efforts and such green initiatives as migrating to alternative fuel options for limousines.