One of the great things about the Navy bureaucracy is that because it is so large, it has to encompass a lot of different peoples needs. Because of this, education resources become open to its members that would normally cost money out of pocket.
Naval Postgraduate School is a classic example. They have SEALs, SWOs, Seabees, Submariners, Supply officers, and a whole host of other people to educate. What NPS has done is create a lot of distance learning programs in order to cater to everyone.
The distance learning programs page is located here. You can drill down to the certificate programs here. Certificates allow you to pursue three-four graduate level classes in a particular field without getting a degree. Some are offered asynchronous, meaning they are 100% at your own pace. Most have registration times and classes that you'll follow with others.
The only cost to you is books. Most of the classes have Navy funding, so you may not pay for anything. NPS is NOT allowed to charge you tuition, so you won't have to file for tuition assistance. The course descriptions are located here, note that doing the Space Certificate Course gets you a VS1 AQD on your record.
The recommend that you review your officer community brief, look at your long-term schedule, and pick a few areas that your community values, but you may not have expertise in. For example, lets say your first tour was on a cruiser and you learned all about Air Defense and AEGIS. Great! But you didn't do a lot of Anti-Submarine Warfare, and you know as a SWO you need some knowledge there to be better rounded and more competitive for promotion. It thus makes sense to register for the ASW certificate, so you can fill in that gap in your knowledge.
If you've already sent your transcript to NPS (in Top Ten for Ensign), then registering for the certificates is easy. If not, what are you waiting for?
