B&H has the Datacolor Spyder5PRO and Spyder5ELITE Display Calibration Systems as its Deal Zone deal for Friday and Saturday only. The Spyder5PRO is now $109 (reg. $189) and the Spyder5ELITE is now $174 (reg. $279). Check them out while the deal lasts here at B&H Photo.
The Spyder5 is an excellent display calibration tool. For more about they system and how it works, read my Spyder5ELITE Review.