Those three ISO's that you downloaded are the entire install for redhat linux 9, minus the source and documentations CD's, like you would get from the store. They include hundreds and hundreds(if not thousands) of applications, including at least one complete office suite, many different text and gui internet tools, including browsers, mail clients, irc clients. Several different desktops. Security tools such as packet sniffers, port scanners, etc. etc. Servers such as apache, samba, sendmail, postfix, mysql, postgresql, bind etc.etc.etc. . Tools for science and engineering, tools for programmers, blah blah blah blah the list goes on and on and on.

There are very few things which cannot be done with only the stuff included on those three cd's.
If you do find somethings that you need which are not available, the links provided above are a very good start for finding things, and of course the ever powerful google.

Good luck, enjoy the journey, for that is what you are about to embark on.