Recently I've found myself in a frustrating situation at the office, and it was ALL MY FAULT!
I love using Scalable Vector Graphics (SVG) in my sites. The graphics can be easily generated directly from Adobe Illustrator, and scale PERFECTLY making responsive design using these images easy. However browser support for SVG images is less than 100%, here is an easy trick for making sure you don't can any of these: showing up on your pages.
Recently one of my application servers developed an intermittent issue where the MaraiDB instance running on it would randomly fail. Apache however would stay up, so when my original status check page was hit by the Layer7 HAProxy check, it would get a valid response from my application.
New Update to this post on 5/3/15: Updated Referer spam blocking code.
I needed a way to get the code base of the sites (Mostly Drupal 7, a few wordpress, and custom coded sites), upload images and other asorted media in sync between the two servers. I looked at the couple common utilities, I've used RSync in the past to maintain backups on other servers, but it has limitations on two way sync on multiple live servers. Enter Unison, it does exactly what the name implies, unifies multiple copies of the same set of files into 2 (or more) identical copies.