OK, I am sure there has to be a program like this out there but if there isn't I think it's a great idea that it be made to close the gap in difficulty in using the Linux shell. I need a program that acts as a database with a list of the majority of Linux shell commands, each command has a description so if you type in a search box, command for metric conversions you'll find what your after. It would be a godsend, anyone know of a program that does this? And I know, you could do the same 'googling' the search but I would like to use this offline.

If you have a distro that you can use apt you just
apt-cache search metric conversions

And you can do it offline.

http://freashmeat.net is a good place to search for programs.

If you want to search the commands you have installed
man -k keyword

May be you can use
In a shell --> $apropos keyword
In GUI --> run xman and select commands section
In KDE --> K-->run --> #command


Wish you all the best!