Not entirely free, you first need to buy the photo editing program that the plug ins will work with:
The Nik Collection has since grown from six to seven plug-ins. It includes Analog Efex Pro, Color Efex Pro, Silver Efex Pro, Viveza, HDR Efex Pro, Sharpener Pro, and Dfine, all of which work in Photoshop, Lightroom, and Aperture.
https://www.google.com/nikcollection/
Windows:
Windows Vista®, Windows 7, Windows 8
Adobe Photoshop CS4 through CC 2015
Adobe Photoshop Elements 9 through 13 (apart from HDR Efex Pro 2, which is not compatible with Photoshop Elements)
Adobe Photoshop Lightroom 3 through 6/CC
Mac:
Mac® OS X 10.7.5 through 10.10
Adobe Photoshop CS4 (CS5 for HDR Efex Pro 2) through CC 2015
Adobe Photoshop Elements 9 through 13 (apart from HDR Efex Pro 2, which is not compatible with Photoshop Elements)
Adobe Photoshop Lightroom 3 through 6/CC
Apple® Aperture® 3.1 or later
GPU Compatibility:
NVIDIA GeForce 8 Series, GeForce 9 Series, GeForce 100 Series, GeForce 200 Series, GeForce 300 Series, GeForce 400 Series, GeForce 500 Series, ATI Radeon HD2000 Series, Radeon HD3000 Series, Radeon HD4000 Series, Radeon HD5000 Series, Radeon HD6000 Series.
If no compatible card is available, GPU acceleration will be disabled and the CPU will be used.