The GTA Leaderboard of sorts opened up in conjunction with the game's midnight release. It's a place that keeps track of your stats, competitions, and Liberty City wide events. For instance, there's a graphic for The Liberty City Marathon. Upon further research, it appears as though the Marathon portion is just a race against fellow socialites to attain specific milestones.
You can also track crime rates with the LCPD Blotter, see how you size up with everyone else once you've completed the game, join the 100% club, join or monitor the Hall of Fame, and track your stats in multiplayer.
Wow! Have you played it yet? What a country! I can't believe I'm at stupid work.
'GTA' Social Club Unveiled