Presentations
Rik Henson's SpmMiniCourse
Written guides
The Human Brain Function book - these are a series of chapters covering theory and to some extent implementation in SPM of the areas below. Be warned that some of these chapters are aimed at quite a high level, and may be hard to follow for those without relevant background.
Papers published by the FIL group on SPM - these are available online via the SPM website, as are some other important papers on related theory.