The LIDC has recently finished the six-session Teaching Portfolio series, which covered the different steps in developing a Teaching Portfolio or Dossier. The sessions are hands on, scaffolded, and rely on the active participation of everyone who comes. If you were not able come, or will attend in the fall, here is a link to a good resource in the mean time.
The Canadian Association of University Teachers has written a comprehensive Teaching Dossier Guide. It was first prepared in 1986, and the most recent update from 2006.
The Guide (download the pdf here) contains a general explanation of what Teaching Dossiers (or portfolios) are, and how it can be used in academia, how to create a dossier (and what to include), and also contains an example dossier.
The focus is on the use of a teaching dossier as part of an evaluation process, and so it stresses evidence, clarity and conciseness. This is a good resource if the purpose of your dossier is for employment or tenure for example.