The first answerer is incorrect. This category is News and Events. Celebrities are often in the news and so are their defamation cases, so I think you are in the right category with your question.
A couple of famous defamation cases were/are:
1. David Schwimmer sued former Hollywood fund-raiser Aaron Tonken alleging that Tonken told the National Enquirer that two Rolex watches were required by Schwimmer in order to attend the charity dinner.
2. Sharon Stone sued plastic surgeon Renato Calabria alleging that he falsely told reporters that she had undergone a facelift.
3. "Wheel of Fortune's" Vanna White sued because someone used a robot-like figure with a wig standing before a letterbox similar to that used by Wheel of Fortune.
4. Bette Middler received $400,000 when she sued for a similar voice that sang on a commercial.
5. Dustin Hoffman, won $3 million from a Los Angeles fashion magazine for a Tootsie takeoff.
6. Robin Williams is suing a celebrity look-alike Michael Clayton and his agent, Michael Pool, saying Clayton is being passed off as the real Williams.
7. The British Sun is being sued by Cameron Diaz over a story that implied Diaz was having an affair with a married man.
8. Nelson Mandela has filed a lawsuit against a former associate in order to protect his name and a number of original paintings that he had signed alleging forgery by his former associate.
9. Famed British couple, David and Victoria Beckham, are suing their former nanny for telling the tabloids that their marriage is in trouble. According to the lawsuit, the nanny's contract contained an agreement not to talk about the celebrity couple's private lives.
10. Cameron Diaz sues a photographer over topless photos. The photographer says he has a signed model release and Diaz says not.
11. Mexican dog psychologist, Cesar Millan, also known as the "Dog Whisperer" is being sued for copyright infringement, breach of contract and breach of confidential relationship.
12. Talk-show host Maury Povich is being sued by his producer for allegations of sexual harrassment in the workplace.
13. Charlie Sheen, star of "Two and a Half Men" is being sued by a woman who is claiming that the wacky, stalker lady next door is modeled after her.
14. TV Producer, Aaron Spelling is suing his nurse for defamation and breach of contract.
15. Jane Pauley is suing the New York Times for invasion of privacy in divulging her struggle with bipolar disorder.
You can easily find much more cases by typing "celebrity defamation cases" in your search engine.