My hovercraft is full of eels! in many languages. You never know when you’ll need this.
Free replacements for many commercial apps are already available. Here is a good list to help you get started looking, once you have your basic Linux system up and running. (Some of these apps will already be bundled with many distros!) If you don’t find it in the list, freshmeat and sourceforge are your friends. A more complete list is available at the advocacy site, Open Source As Alternative.