We have PostGIS intro presentation we did in September in 4 parts at https://www.youtube.com/playlist?list=PLHPJPLnP-bUWZShKrUIdbJM5dig8oavzQ.
In the Intro we covered PostGIS geometry, tiger geocoder, and raster. Sadly we didn't have time to cover geography or topology.
Code used in the presentation can be downloaded from our presentations page: http://www.postgis.us/presentations