you dont have to stream at HD quality...and with your laptop, you may not be able to anyways. depends on how old of a laptop it is (processor power)
you should check out ustream.tv its a 100% free service. I was using it myself, until i got sick of the ads that popup over the video. my solution was to use the petdragon.info site to host the flash "player" while using my home bandwidth to distribute the content. which i could do from the site and just push the stream to the server.. w/e to many details probably.
I would sujgest though, reguardless of your processing power available, to look at getting a webcam with a built in encoder.
http://shop.skype.com/webcams/high-quality/iss-talk-7140/
or better
http://www.facevsion.com/en/modules/tinyd1/index.php?id=12
This will reduce the amount of processing your laptop will need to do and also reduce heat and power consumption as well.
there are MANY other webcams out there, but ALL rely on your processor to do the work.
Other webcams that i would recommend if you have the processing power,
Great 16:9 widescreen wide angle
http://www.microsoft.com/hardware/digitalcommunication/productdetails.aspx?pid=008 I loved this cam and the quality it gave...Norbert decided to throw it in the sand and the camera stop focusing.
the one i currently have, only because of the mounting options:
http://www.microsoft.com/hardware/digitalcommunication/productdetails.aspx?pid=016 its fixed focus, so up close its not that great.