Here’s my updated list of sites I prefer when searching for FREE Stock Photos:

StockSnap.io

Hundreds of high resolution photos added weekly at StockSnap.io.

Unsplash

Unsplash features a great cache of photos organized by category. They also have plugins for direct integration in Photoshop and other popular graphics softwares.

Pixabay

Search through a library of over 1 million stock images and videos at Pixabay.

Photo by Benjamin Voros on Unsplash