For ericgrysko.com, I installed and configured varnish 3.x on my EC2 app. server behind my ELB. My storage file is stored on the ephemeral SSD on my instance. I use the Drupal varnish and expire modules to purge node cache. I have basic familiarity and understanding of VCL.
At work, I have assisted in troubleshooting an ancient varnish install in a Drupal 6 stack.