If you're trying to study concepts, it's a different case. You study the concepts, not specific technologies.
An example would be MVC. There's a lot of MVC frameworks that's out there. If you want to pickup on MVC, just choose among the MVC frameworks - Groovy/Grails, C#/ASP.MVC, PHP/CakePHP, Ruby/Rails, etc. etc. again, stay away from hype and language/framework vs. language/framework debates. If you pick one you're comfortable with, the concepts transcend language and time. If your career moves you on to another language, you'll find MVC is 'almost' the same save for minor differences that is brought upon by the languages themselves.
Especially applicable for the number of JS MVC Frameworks popping up every 3 or so months.
Point is, get really really good at one or two things and you'll be able to transfer easily. Doesn't matter what those one or two things are.
I suggest you find a "stack" (for want of a better word) and become comfortable with that and why it exists. Maybe this is the traditional RDBMS - Webserver - JS. But be surte you understand it, can deploy it from scratch, know where and how packages interact.
Then start extending that stack - maybe email integration.
You will get a feel for why technologies exist when you hit the limitations of the old ones - and the best way to do that is to package up the old ones in your head and suddenly you will get a new idea for improving it. THere is almost certainly a project on github for that but no matter - now you know you are at the edge of the art and can keep expanding.