Colin McRae was rumoured since the launch of the Dreamcast. However not much was ever mentioned with respect to its development, at least not to the magazines I was buying. It would be interesting though to see if the rumours where even true, and if yes, where they planning to implement "just" a port or something more pumped up for the Dreamcast version?
Given that the announcement of the Dreamcast withdrawal found many games under development, there should be many games out there implemented to a certain extend. I once read that a SDK sold on ebay contained work in progress for Ecco 2 for example.