The internet is pretty much endless.  You can find any kind of information for any topic you can possibly think of.  Or at least that's what I thought when I was in college, where I consistently reached dead ends when searching for math and engineering topics.  If I was looking for information on a particular equation or a method of solving a problem, I'd usually get a few results from Ph.D. papers and patent applications, most of which charged money.  (As soon as I see a search result that asks for money, I press the back button and usually never look at that site's results again.)  But there was definitely a void when it came to these topics. 

That changed somewhat recently, and I'm not really sure why.  Sites like Wolfram MathWorld and even Wikipedia have extensive amounts of information about highly specialized topics in engineering and math.  These sites usually mimic the things found in a typical text book, but occasionally they'll take it a step further and even link to related topics.  It's gotten to the point where I regularly use these sites as references because they've proven themselves to be so reliable.  It's good to be able to have another source of information when I reach a dead end.  Hurray internet!