I stole this list from static_X3. It has most of them in it I think.
Fox Creek
Eagle MTB Park
Craigburn Farm
Lynton
Shephards Hill
Sturt Gorge
Flinders Uni
Prospect Hill
Kangarilla
Kersbrook (devils gully)
Chain of Ponds (bennets)
Cromer
80 acres
Onkaparinga Gorge
Cleland
Pioneer Womens Trail
Bullocks
Mylor Postie Track
Anstey Hill
Cobblers Creek
Dry Creek linier reserve
I reckon Fox Creek, Kangarilla and Lynton/Belair are your best bet for jumps and drops in that order.
There is also a DJ park in the city center if you are into that sort of riding.