How to automate post-installation setup of a distribution?

As you all know, setting up a fresh installation of a distribution can be time consuming. Manually installing and setting up various packages and apps takes a lot of time, even with all the dotfiles on hand. Thus recently I have been wondering about whether there are any tools/best practices concerning the automation of this process? Are there any universal tools? Or should plain ol' shell scripts (for different distros/hardware configurations) be plenty enough? Here's a link for some more information on this topic. Author's post-install shell script contains ~2000 lines of code.