This article on one of Barack Obama's hobbies is pretty fascinating. It turns out that Obama is a member of a group of guys who love to get together and play basketball. It just happens that this is a remarkably influential group of guys. And those connections indicate the breadth of Obama's own political growth.
Some of those he plays with include Arne Duncan (CEO of the Chicago Public Schools), Alexi Giannoulias (Illinois State Treasurer), Martin Nesbitt (Chairman of CHA), Craig Robinson (Brown's basketball coach and Obama's brother-in-law), and John Rogers (founder of Ariel Mutual Funds, the largest African-American owned mutual fund company). Interestingly, Duncan hails originally from Harvard, IL and played basketball at Harvard and then professionally in Australia and Rogers and Robinson were basketball teammates at Princeton. Duncan and Robinson were also members a couple years ago of the national Hoop It Up 3-on-3 basketball champion team sponsored by Rogers.
Some familiarity with Chicago politics allows us to see that with Duncan's connections to Mayor Daley, Rogers' connections to Jesse Jackson and Bill Bradley, and Giannoulias' connections to Governor Blagojevich, Obama has quite the network via these pick-up basketball games.