SAN FRANCISCO (CBS SF) –You’ve heard of Black Friday. You probably checked out the Cyber Monday deals. Maybe you even headed downtown for to pick up some presents on Small Business Saturday. But on Tuesday a completely unselfish movement is vying for your cash.

Welcome to #GivingTuesday.

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The hashtag #GivingTuesday used to identify posts about the event will get more notice Tuesday than the website, givingtuesday.org.

Two years ago, 50 million people posted to social media about the event, and those numbers only grew last year. You’ll see examples of giving, and suggestions of who to give it to. On Instagram, instead of the ubiquitous “selfie,” you my see photos labelled “#Unselfie” showcasing people giving back.

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In the San Francisco Bay Area, charities like Cancer Prevention Institute of California are using the day to raise their profile and reach new donors. The United Way of Northern California is kicking off a 12 days of Christmas fundraising drive to help pay for their efforts. Shelter Providers of Northern California are hoping to use funds from the day of giving to build new homeless shelters.

Many charities have matching donors lined up to double the value of gifts received today and through the season…

The concept began with New York’s 92nd Street Y.  Since then, the United Nations Foundation joined as partners to spread the word.  Social media accounts caught on, and spread the word virally, and an instant day was born.  This year, it should be even bigger, with more corporate partners, more 501(c)3 charities registered, and more social media networks.

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Many charities are posting their efforts to the main Facebook page, facebook.com/GivingTuesday or just search the hashtag #GivingTuesday on your favorite social network.