Tim Mattson (Intel), has authored an extensive series of excellent videos as in introduction to OpenMP*. Not only does he walk through a series of programming exercises in C, he also starts with a background introduction on parallel programming.
Check out the series: https://www.youtube.com/watch?v=nE-xN4Bf8XI&list=PLLX-Q6B8xqZ8n8bwjGdzBJ25X2utwnoEG&index=27
The slide set can be obtained here: http://openmp.org/mp-documents/Intro_To_OpenMP_Mattson.pdf
The exercise files can be downloaded here: http://openmp.org/mp-documents/Mattson_OMP_exercises.zip