Years ago my mother insisted that our family join in the boycott of Nestle's products. Don't remember that one? It was because Nestle sold baby formula to third world countries, a formula that they knew poorer families could not afford and would buy anyway (but mix it with unsanitary water or dilute it beyond being nutritious). Back then, mailings and buttons and bumper stickers were the way one spread the word; in this case, successfully... for a time. Nestle continues to market its formula and in 1988 the boycott was reinstated. Still haven't heard about it? Well, now you have.
I don't remember when I first heard the phrase girlcott, but its the opposite of boycott: you buy the company's products, not avoid them. Here's an example.
Over the weekend, calls started for a boycott of Amazon. Why? Because apparently they're removing books from their sales ranking - books that fall into a GLBTQ area. Books like Well of Loneliness and Brokeback Mountain. Now, this isn't the first time that there have been calls to boycott Amazon. However, the viral spread of this via Twitter has meant that major news outlets heard about it within hours, Facebook had a page up quickly and an internet petition was started over on Care2.
I remember the Divest Now movement (now being appropriated for both Darfur and Israel)... I even remember the peace marches of the 60s.
The causes change, the technology changes, the passion remains. Get involved.