Lincoln Mullen has written a great series of workshops on the Spatial / Digital Humanities over five days. Day 3 is focused around Georectification with Mapwarper.net and is a very good tutorial.
The full workshop contents are here, and I recommend you to check them out:
Day 1: Introduction and Setup | Map Literacy | Narrative Maps
Day 2: Data Maps | QGIS
Day 3: Georectification | Working with Spatial Data
Day 4: Deep Maps | From Manuscripts to Maps
Day 5: Programmatic Maps
The link to the Georectificaiton Workshop is here: http://lincolnmullen.com/projects/spatial-workshop/georectification.html
The screenshot of the tutorial is below the fold.