There's some great singletrack up in the hills of the Arapuke Forest Park...
If you're a beginning or intermediate rider your best bet is to go up to the Scott Road Car Park. Check out the trail map there or even better, download the latest map from the Manawatu Mountain Bike Club's website: http://www.mmbc.co.nz/ Once you've mastered the easy Jack Frost trail give Riff Raff and About Time a go. They're excellent intermediate trails that flow nicely. Jack Be Nimble is another that has some great moments including a few big swooping berms.
Advanced and expert riders will prefer to park at the Kahuterawa Car Park and ride up the steadily climbing four wheel drive track called Back Track. Alternatively ride up Zig Zag Road which is more direct but steeper. Rocky and Rambo are two short trails you won't want to miss before you tackle the outstanding new downhill track that goes down beside Zig Zag Road. It's got all the modern fun stuff including drops, flat tops, gaps and swooping berms. It's steep in places but it's more like a fast and fun down sloping trail than a typical steep downhill trail.
The Arapuke Forest is visitor friendly with good signage and map board but the club is actively developing trails so best to download the latest trail map from http://www.mmbc.co.nz/where-to-ride/arapuke. There are toilets at the Kahuterawa Road Car Park.