One To Watch: MarioKart: Source
In one of those very unlikely cases, a mod for Source which has aimed high and, survived despite 4 long hard years of development and, which is still going strong. Despite showing positive signs of progress with a news post today on ModDB it still looks a long way off. If you can support the mod in anyway and want to help then you can see what positions they are looking for here. You can also check them out at ModDB or on there website.