I have just started poking around OSM in the interests of adding local hiking/mountainbiking trails. I have noticed that there is a lot of trail data available in Massachusetts from MassGIS and DCR. For instance, there are a lot of trails in the DCR state forest that I don’t see in OSM: http://bit.ly/1LekCKS
SomeoneElse: Absolutely for trails that aren’t mapped yet (and there are plenty around me), but since DCR has so kindly done all this work, we might as well use that to start with.