Like BaLa said scanamerica.us is probably the best place to start, I have 2 feeds there and site is very easy to navigate and monitoring is easy. plus you could even monitor through there on your cell phone too if you have a data plan. St. Charles County, Missouri Live Police, Fire, and EMS Scanners the top two are my scanners, I have two units streamed.if you need an example of what you can hear.
To make it easier for local people to monitor law and ems/fire I made another page. ParamedicCyberBase Scanners
Good luck and enjoy.
I think if you read through some of the threads in the Streaming / Broadcasting / Audio Recording Forum you may find what you are looking for or at least be directed in the direction you want to go. Post your questions about feeds, etc there.
jos, there are 3 places to see if there's an online scanner for your area; you didn't enter your city/state (and you should - go up to the User CP in the upper left corner of the lower tool bar), so it's hard to know where you are looking...(note anything in blue is a link)...
This link lists sites with multiple state feeds...