Hey Kirkby,
I too am a rider, sort of vice versa though.. started more into riding before fishing but nowadays my free time is taken up by fishing! no more riding =|.
If in sydney, XC.. Manly damn is a nice intermediate flow. Downhill.. Menai has some great hills with knarly jumps i hear and also for a quick hit you can try Kentlyn national park. There's a handfull of trails in Canberra weather that be XC or DH .. Mt Stromlo for epic D/H.
Cheers,
Teo