Here you are a video tutorial to learn how to use bUnwarpJ, a plugin for consistent and elastic 2D image registration. Find more information at its main site http://biocomp.cnb.csic.es/~iarganda/bUnwarpJ/
This tutorial was developed for bUnwarpJ v2.0. Although new versions of the plugin have been released, it is still a good reference to know hot to get started with the plugin.