Some free Nik Tutorials.
"Now that Google has announced that the Nik Collection is free, we decided to make the GreyLearning courses related to the Nik Collection free as well. This bundle includes courses on the basics of using the Nik Collection, Viveza, Silver Efex Pro, and Analog Efex Pro"
You do need to enrol - not sure what that entails as I haven't yet followed through.
Original post about free Nik SW.