This is forked from someone else; I've yet to go through this and fully customize it but I thought it was such a great idea I had to steal it.
Custom recipe to get OS X 10.10 Yosemite running from scratch, setup applications and developer environment. I use this gist to keep track of the important software and steps required to have a functioning system after a semi-annual fresh install. On average, I reinstall each computer from scratch every 6 months, and I do not perform upgrades between distros.
This keeps the system performing at top speeds, clean of trojans, spyware, and ensures that I maintain good organizational practices for my content and backups. I highly recommend this.
You are encouraged to fork this and modify it to your heart's content to match your own needs.