Cameron Diaz [1] may have found a new boyfriend. The actress hit the gym last Friday with Good Charlotte guitarist (and Nicole Richie [2]'s brother-in-law) Benji Madden, sparking rumors that the two have started dating. The two certainly have been spending a lot of time together, as their gym trip came the day after they both attended an A-list book party in LA [3]with Nicole; Benji's brother, Joel Madden [4]; and Cameron's pal, Gwyneth Paltrow [5]. A source said that Benji has been spending a lot of time at Cameron's home [6] and that the actress "seems very happy" with the musician, adding, "He is the nicest guy and treats her like a lady." This isn't Benji's first time getting involved with a famous woman, as he has previously dated Australian starlet Sophie Monk, Paris Hilton [7], and Holly Madison. He was also recently linked with Miley Cyrus [8]. Cameron, for her part, also has a history with musicians, having dated Justin Timberlake [9] from 2003 to 2006. The two were so close that they have even remained close friends [10] after they split.