In the most recent edition of the Glimmer Train bulletin, I loved this article by Cary Groner on conflict. Here's a small snippet:
I've been surprised, when reading books about fiction writing, that such short shrift is often given to the decisions writers make about conflict and its levels. We hear a lot about voice, point of view, characterization, place, structure, theme, and other issues; but when conflict is discussed, it's rarely treated as particularly complex. You'll read, almost as an afterthought: 'Of course, your story must have conflict,' as if it appears in unvarying form in every narrative. But conflict is no more monolithic than love is; and in the same way that love arrives in multifarious forms in both life and literature, so does conflict.