I will present a detailed account of important recent developments in the rapidly evolving area of glass transitions in thin polymer films. First I will review the case of polymer films supported by substrates, and show that a definite experimental consensus exists. I will then consider recent results from experimental studies of free standing films of polystyrene. These studies (motivated by the original work done in Guelph!) have provided a thorough quantification of the behavior of glass transition anomalies in free standing polymer films, and have served to motivate recent attempts at theoretical descriptions. Finally I will examine models which have been proposed to explain the experimental observations and discuss the significance of these models.