On the website http://www.pst.informatik.uni-muenchen.de/spring-school99/ of the Spring School on Categorical Methods in Logic and Computer Science held in Munich in 1999 you can now find two online tutorials Sheaves by Giuseppe Rosolini Fibred Categories by Thomas Streicher that can be downloaded in PostScript format. The tutorials are introductory but assume some basic knowledge of category theory. On behalf of the organizing committee, Bernhard Reus