This sewer-cam video from Raleigh, North Carolina has been inspiring nausea all over the web. Deep Sea News contacted experts to find out what kind of creature this could be.
They are clumps of annelid worms, almost certainly tubificids (Naididae, probably genus Tubifex). Normally these occur in soil and sediment, especially at the bottom and edges of polluted streams. In the photo they have apparently entered a pipeline somehow, and in the absence of soil they are coiling around each other.
Read more about annelid worms and see more videos, if you have the stomach for it. http://deepseanews.com/2009/06/creatures-from-the-sewer/ -via a comment at Digg