There are two large areas of Pine Forest in the Waitarere settlement, appropriately named North Forest and South Forest.
North Forest
Malcolm and I went for a wee hoon around the roads one Sunday afternoon. The terrain is soft and rolling: good riding if you can stay on hard-packed pine needles where MTBers have been before. A lot of the track had been cut up by motocross bikers: once you pierce the pine needles it is sand underneath and almost impossible to ride.
About 2km in on the eastern side right by the farm fence we found some beautiful fast single trail winding through the trees. It was a real pleasure to ride.
South Forest
Tom, Blake and I cruised up one Saturday afternoon after unicycling club. There is a 3km loop track that goes up the narrow strip of goblin forest (dark, close packed pine trees) beside the beach. Its mostly hard packed and very rideable. A good track for first time Muni riders 'coz theres lots of trees to lean on to get started again.
If you time it right, you can pop out over the dunes and walk around the wreck of the Hydrabad.
Getting There
On SH1 between Levin and Foxton, turn towards the coast at the Waitarere turn off. Drive for about 10km until you reach the township. For the North Forest, turn right at the old petrol station and park in front of the gate. For the South forest, go a bit further through town and turn left at the dairy. Go all the way to the end of that road, and turn right onto Hydrabad road. Take the first left and park there (you can't miss the forest!)