Other
Elated Communications: Perl and Cgi Scripting
This series of tutorials, teaches you how to write CGI scripts such as form mailers and guestbooks, using the popular Perl scripting language.
BBC
Bbc Bitesize: Data Structures and Data Types: Identifiers and Annotation
See how choosing meaningful names for the variables, constants, and subroutines makes it easier for the next person to work on the code to understand it.