Celebrate Earth Day with free coffee

Friday (April 22) is the 42nd annual Earth Day, so let's drink to that -- with free coffee at Starbucks or Caribou (or both) in a reusable cup.

• Bing:Earth Day 2011 -- A Billion Acts of Green

Free coffee is one of several free things you can get as we collectively pay homage to our planet and rededicate ourselves to protecting her health. Remember that not all stores participate in national deals, so you might want to call ahead first.

Here are details:

Bring a reusable tumbler or mug to Starbucks and get a free hot or iced brewed coffee or tea. Those without a mug can get a 20% discount on a Starbucks model. "What if you can't bring in a mug and don't want to buy a new one? That's okay too," Starbucks said on its website. "Just request your coffee or tea in one of our 'for-here' cups and we'll pick up the tab." 

Starbucks also shared this eco fact:

Although reusable serveware and tumbler use still only accounts for a small percentage of total beverages served, those of you who did bring in reusable mugs still made a significant impact. In 2010, people brought their own tumblers into our stores more than 32 million times, keeping nearly 1.45 million pounds of paper out of landfills.

That's a promising start. Another reason to bring your own mug: You get a 10-cent discount on Starbucks drinks any day of the week.

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Caribou Coffee is offering a similar freebie on Friday -- free coffee if you bring your reusable mug. The company's Facebook page also says: "And don't forget, you can save $.50 each and every day by bringing in your favorite mug again and again. It's our way of saying Happy Everyday and promoting sustainability." Starbucks, take that.

Numerous deal sites reported that Whole Foods is offering free coffee too. However, Earth Day celebrations will vary from store to store, so check before you head out. Post continues after videos about other "green" ideas for Earth Day and every other day:

More Earth Day-related freebies:

• Lowe's is giving away 1 million free trees on Saturday, April 23. The giveaway, in partnership with American Forests, is on a first-come, first served basis, and we suspect a million trees will go fast. Scan the barcode on your tree with a mobile phone to watch a video on how to plant and care for it. It won't help the Earth if you over- or underwater your tree and kill it. Lowe's says:

When planted, these one million trees will eventually produce more than 260,000,000 pounds of oxygen annually, providing air for more than 670,000 people for one year.

• A free reusable bag can be had from Kellogg's with the proof of purchase from two boxes of cereal. You'll need to use this form (.pdf file). There's a limit of five bags per household.
• Disney Stores are giving away a free reusable shopping bag on Friday to those who bring in five plastic shopping bags for recycling.
• Evos is giving away a free organic milk shake. No purchase necessary.
• Swap a skin care product -- full or empty or somewhere in between -- at any Origins counter on Friday for a free full-size tube of Checks and Balances or A Perfect World facial cleanser. Take this form along.

Don't forget to look for special Earth Day freebies, deals and activities specific to your city or town. For instance, Southern California Public Radio had this roundup.

Also, national parks that normally charge admission are free this week through Sunday, April 24.

Finally, Tuesday, April 26, is National Pretzel Day. Sing for your snack or say "National Pretzel Day" for a free pretzel at participating Pretzelmaker stores.

More on MSN Money:

• 4 foolish ways to go 'green'
• Going -- and saving -- green on entertainment
• Going -- and saving -- green in the kitchen
• 8 cheap ways to save on gas
• Fact or fiction? 8 gas-saving myths
• Restaurants that take their eco-friendly commitment beyond what's on the plate