You might be interested in the "Advanced Bash Scripting Guide" on the www.tldp.org
website. Don't let the "Advanced" scare you. It is composed entirely of examples you can try yourself.
Look on the gnu.org website for documentation on the core-utils package. This package supplies most of the files in /bin.
Another way of getting documentation is to produce printable ps or pdf files from the info source files. If you download the source of a package, and run "./configure" in the source directory, there is often a "make pdf" or "make ps" target that will generate a more readible version of the info documentation. Some packages have a <package>-doc version. For example, samba-doc supplies 4 full sized books on samba 3 which are the same ones you can buy in the book store.