Good deal on the WD Blue 8TB 3.5" Internal Hard Drive from Amazon US.
ATA-600 5400 RPM Class, SATA 6 Gb/s, 256MB Cache, 2 Year Warranty
Promo code for 7% off for two.
I needed more room for my Linux ISO collection and these drives should be ideal.
Suitable for desktops, NAS at a pinch, but not suitable for surveillance systems.
FYI - CMR drives - Suitable for NAS.