Principles of random effect analyses
These analyses are also called second level analyses, and concentrate on the variation of activation between subjects in deciding the significance levels for SPMs.
See also the RFX section of the FIL/SPM bibliography.
There is a nice random effects discussion on the Wisconsin site
A useful set of powerpoint slides on random effects, by John Aston, at the MRC Cyclotron Unit.
Jesper Andersson's nice talk on Mixed effects models and variance components.