There is a group that does ride a few "local" places. I cannot remember what they are called but I ran into them once up at Mid Michigan Community College. I think either Rays, or B-Xtreme in Midland may have more information about group rides. Myself, I'm in Bay City, & I usually rotate between Mid Michigan, Ithaca Jailhouse, Gladwin County Park, Ogemaw Hills Pathway & Rifle River Rec Area. I try to hit one of these places weekly as each is about an hour drive from my house. Send me a PM if you want to try to get together & ride.
2013 mtb trails - Midland City Forest, Gladwin County Rec Area, Jailhouse Trail, Ogemaw Hills Pathway, Glacial Hills, Rifle River Rec Area, Hanson Hills, Hungerford Lake, Burchfield, Bennett Park, VASA Singletrack, Mid Michigan CC, Potawatomi, Big M, ILRA