Hey Pepsi,
There is a huge online community around exchange based betting sites. The big one in Europe is Betfair. The idea is you can place a bet for and against an event which allows a host of different strategies to be played to manage your risk. A lot of the guys online use pseudo-statistics and probability but over the last few years with the boom in Poker and sites like Betfair normal retail guys have got a lot more sophisticated and now are closer to mimicking financial entities that deal copious amounts of securities.
Then of course there are the regular Las Vegas type of betters who gamble with an element of risk management ideas. I say gamble, but with their astronomical wealth of knowledge of say a sport is unthinkable to us casuals, they would say they have an edge.
Lastly we have nabs who bet every game week for their chosen sport/event. Some for a punt to make a quick buck, some of the joy of a gamble etc etc.
So some sites:
Slightly more sophistacted betting found here:
http://www.geekstoy.com/
I use this application to some times trade on trends in large sporting events that attracts lots of bets, check their forum, (this means I open and close my "bet" before the event even starts)
Guys who take their betting on sports slightly more serious than the average guy:
http://forum.sbrforum.com/
And for anyone else who bothered to read this and wants a nice noob friendly intro to risk managing betting check out this site:
http://drbobsports.com/essays.cfm?cat=0
Disclaimer: I am in no way liable for nabs blowing their grandparents inheritance on sports bets.