Online CentOS administration courses / resources?

https://www.lpi.org/ is a good distribution-agnostic certification, the syllabus will give you a good framework for self study. The Nemeth book is good, I have it. Teaching yourself in a crash course is near pointless in my experience, this is only useful for cramming for a test and without repetition or practice you won't retain very much. This stuff takes time to sink in and practical situations to apply the knowledge in. Experienced sysadmins haven't crammed for a few weeks they have worked at the coalface for months or years.

The Digital Ocean documentation is outstanding. You could do a lot worse than to just work your way through the articles linked https://www.digitalocean.com/community/tutorials/?q=centos. Having done this professionally, I personally would not pay for any certification or courses. Start with the Digital Ocean docs, then pick up a book on the subject (the http://www.amazon.com/exec/obidos/ASIN/0131480057/metafilter-20/ref=nosim/ is a classic, although I can't speak for the quality of the 4th edition in particular). http://www.amazon.com/exec/obidos/ASIN/0596003307/metafilter-20/ref=nosim/ also might come in handy.

The ultimate application of the knowledge will be managing a handful of public web servers behind a load balancer hosted at a company like Rackspace. Do you already work there or is the goal to get a job doing this? I ask, and think that it's relevant, because if you already have the job and just need the skills that might lend itself to a different path than if you want to do this for a resume line in order to land a job. In the former case you just need knowledge, in the latter case it may be equally important to get some sort of certification, basically some organization's imprimatur that you can show to recruiters. If you don't need the certification I would not pay for one; I think the courses built around certs tend to do a lot of teach-to-the-test stuff that is pretty low-value otherwise. But it is also difficult assess technical knowledge so I wouldn't go so far as to say they have no value. If you do need the resume lines, I can vouch somewhat for the http://training.linuxfoundation.org/linux-courses as being pretty well designed.

Red Hat has some of the best training and certification classes I’ve seen. They’re well worth the cost, and anything that Red Hat provides will be 100% applicable to CentOS as well. If you have some prior experience there used to be - and probably still is - a fast-track class that includes the RHCT and RHCE exams in one session.

2nd RHEL classes online - they are the industry standard.

Not sure I can fork over $2k or more for them, though :( This is to help prep for a duty I have to take over, not a job I'm trying for.