50 Cent is one of the more famous of the American Gansta Rappers. One can look at the lyrics and underlying attitudes of the genre and form (whether we call it Hip Hop, Gangsta, modern music or whatever) in two ways.
1) As a glorification of the drug taking, misogyny, homophobia and prediliction to violence in the current urban culture of the Unisted States.
2) As the desperate cries of an underclass screaming in both pain and rage at the way in which they are oppressed.
Which approach you prefer is up to you really.
The official 50Cent website is here.
This website is similar but also offers the opportunity to buy his albums online.
Another fan site which includes message boards, and the MTV site includes video of his appearances on that network. There is also a complete collection of his lyrics online here.