I found these two Crest 3D Whitestrips on clearance at Ultra, marked down from $42.99 to $9.99.  Keep your eyes open for similar deals at Target, Kmart, etc.

But if you’d rather getitnow, Amazon has a kick-ass promotion on Crest whitestrips right now:  Buy the Crest 3d White Professional Effects Teeth Whitening Strips 20 Count (40 strips) for $37.22, “clip” the $7 coupon and then submit this MIR for $10 back!  Or choose the Crest 3d White Intensive Professional Effects Teeth Whitening Strips 7 Count for $39.55, “clip” the $7 coupon and submit for the same $10 MIR!  These are the one-time only prices – choose Subscribe & Save to take another 5% off and get FREE shipping (if you don’t already have Prime).  Remember, you are under no obligation to take any other shipments.  You can cancel at any time without penalty.