Rapper Lil Wayne is a tennis fan. I remember he wrote an article for ESPN or other American sports broadcaster previewing the US Open in 2009 or 2010. Nadal was his favourite player at the time. Also, Snoop Dogg was a fan of Ivan Lendl.
Seems that the rappers can't get enough of tennis, also given that Jay-Z was supporting Nadal at RG 2010 and also Wimbledon that year, and Puff Daddy sat in Djokovic's box in the past 18 months or so at one of the slams (US Open?).
Also, Kaley Cuoco (Penny off Big Bang Theory) used to play to a decent-ish level as a junior. She occassionally tweets about the game too. She was cheering on Nadal in the 5th set against Rosol, and also tweeted when Roddick announced his retirement.