Followers: 1.4 million
Sample tweet: "Good morning/afternoon/evening/night. Wherever you are in your day, I hope you're laughing. Loudly."
The former star of Who's the Boss and Charmed may be one of those rare actors who's become more popular on Twitter than on TV or in movies. But before you follow Alyssa Milano, be prepared for tons of tweets. "I tweet a lot. Consider yourself forewarned," she writes in her Twitter bio, and she's not exaggerating — expect a post at least every hour. But Milano's posts feature actually interesting links that don't have much to do with the actress's life, along with the occasional pop-culture nugget. Look forward to lots of baby-related tweets, as Milano recently announced she's pregnant — and has shown she's not afraid of a little oversharing.