Front: 146 lbs/in (25.5 N/mm)
Rear: 268 lbs/in (45 N/mm)
Got it from SL: http://www.scionlife.com/forums/viewtopic.php?t=35024
TRD spirngs have a suprising high rear spring rate (~324lbs/in) for the rear, but the front is close to stock so it should give a sportier but still comfortable ride.
Tanabe is interesting because their rear spring rate is lower than stock, haha.