The official YouTube channel of the Sundance Film Festival is currently screening plenty of shorts, including Gowanus, Brooklyn, which was expanded in to the 2006 feature Half Nelson.
It won the Short Filmmaking Award in 2004 and led to director Ryan Fleck and writer-producer Anna Boden going on to make their debut feature.
> Half Nelson at Wikipedia and IMDb
> Interview with Ryan Fleck and Anna Boden about Half Nelson from 2007