Wanted to share this new discovery; Quizlet has flashcards on some Server facts. Most are oriented to newcomers, but there are one or two decks that delved into the technical side.
'Basics of Server and Web Server Administration' deck seemed a bit bland, but covers the basic need-to-knows.
'Ubuntu Server Guide' gets into the technical side of things. e.g. watch -n1 cat /proc/mdstat - watching the status of a syncing drive.
For anyone interested in studying on the go(iPhones) they do have a mobile app, but not for Android. Android users could use Learn2Leitner
which is integrated with the Quizlet service.