Alyssa Milano, TwitterIf a tweet about malaria crossed your Twitter account this week, there's nothing random about it. It's a focused effort by celebrity tweeters and others to spread the word about World Malaria Day (#endmalaria) and the need for nets to keep the disease at bay. A similar Twitter campaign took place one year ago this week.

Between tweets and retweets, there's no telling how many lives the Twitterverse has saved. It may be one of the greatest forces for grassroots charitable endeavors in history, and much of it can be traced to celebrities who use their Twitter powers for good in the world. I love that, and make a point to seek out and follow those with a positive message.

Sure, they're like most of us out here, using social media to promote a project or business, but some manage to do both at the same time. Take Alyssa Milano, for example (@alyssa_milano), who has 800,000+ followers at this writing and even created a Twitter Philanthropy List.