Some online resources I found useful:
High-Resolution NMR Techniques in Organic Chemistry(2nd Edition) by Prof. Timothy D W Claridge. If you have subscription to Tetrahedron Organic Chemistry, you can download it from there. The newer 3rd version has been out too.
Links to some NMR groups I like to follow:
Bruker NMR Guide(last version compatible with Topspin 3.0) by Dr. Teodor Parella at Universitat Autònoma de Barcelona. His group has also developed many NMR pulse sequences for small organic molecules.
Spin Dynamics Lecture by Prof. Ilya Kuprov at the University of Southhampton. If you are interested in thoroughly understanding NMR from quantum mechanics, and want to play with some simulation using Matlab,this'd be a good place to start.