Have you considered getting Apple IT Pro Certifications? Check and see if there are any Apple Certified Training Centers in your area (there's one at 2333 - 18th Avenue NE Calgary AB).
From a *NIX perspective, you may want to take LPIC courses and get some of those certifications. I've heard that they're not pushovers by any means.
Knowing more about networks in general is never a bad thing. Pick up some good books like Network Warrior or some Cisco Press stuff. Maybe study for a CCNA.
I don't want to sound like I'm heavily pushing certifications, but if you're going to learn a thing, you might as well get a pretty piece of wall decoration to "prove" it so that you can have greater potential opportunities for job hunting. Furthermore, sometimes the structured approach to studying for a certification can open your eyes to areas that you didn't know that you didn't know. After that it's as simple as following your fancy to illuminate the dark spots.
Individual software products like Nagios or Groundwork will have vendors that offer training for how to use those products. I wish I could take some of these courses. Pick a monitoring solution and then search for someone... anyone... who is offering training.
As for learning about DNS, failover, RAID, and etc, here are some tips:
- Find a learning center in your area and peruse the class schedule. New Horizons is just one example of a technical learning center. However, there will also be localized technical learning centers that you should seek out and ask about available classes. Sometimes technical consulting firms also run classes. Talk to them about what they offer; tell them what you're interested in and they might be able to make suggestions even if they themselves don't offer anything quite like what you want.
- Search out and attend user groups in your area for technologies that you are interested in. If for no other reason than asking how those people learned what they did. For instance, find a storage-networking user group, or high performance computing group or whatever else might be interesting to you. Show up to meetings and ask questions about further learning.
- Be resourceful. Network with anyone in the area that has more knowledge than you and ask how they did it and where they got trained. Maybe they "bootstrapped" themselves... or maybe they didn't. Can't hurt to try. Sometimes the best training is received over coffee and Biscotti.
- Don't rule out Cocoa and web development. Hopefully your boss is interested in keeping you happy to some degree and might spring for it. It can't hurt to try... right?
The type of study that you should be looking at can only really be determined by you. It all depends on how you learn. Do you respond better to classroom instruction? Self paced kits? Practice exams? Practical projects? A blending of them all? As an example, I tend to prefer actually working on a project and reading books, articles and forums. However, once in a while taking a full 5 day course can kick me in the rear and knock off some complacency. Keep in mind that it does look better, from a careerist's perspective, to say that you've taken real structured courses on a topic rather than simply stating "Yeah, I've bought and read some books from Amazon on that," (even though the latter is oftentimes better than the former).
Finally, stick around and let us know how it all goes. =)