Site includes Bruce Barnett's tutorials on UNIX shell programming and various other arcane subjects.
Shell Quotes - How to use quotes in a shell script.
Regular Expressions - Written for Solaris, so your milage my vary..
SED - The Stream Editor - Editing a data stream.
Bourne Shell - Everything you wanted to know.
AWK - The basic power tool for UNIX.
Csh - The C shell - warts and all. But before you read that, perhaps you want to look at the next two essays:
Top Ten Reasons not to use the C shell - My essay on the disadvantages of using the C shell for Programming
Tom Christiansen's essay on C-Shell programming
Find - Finding files.