Finds the limit, not at a point, but over the indefinite interval.
It's actually possible to do some serious Math without being grim about it -- it can even be fun!
Recommendable Tools
Mathematica
While I haven't tried this myself yet (there's a free trial download out now too!), this is supposed to be one of the most powerful tools out there for exploring everything mathematical to your heart's content. No syllabus, no pedagogy, no videos to watch -- nothing comes between you and the Math but learning how to use the notation unique to Mathematica, which is not really asking much for all the power and flexibility that should result.
Wolfram Alpha
An excellent way to explore Math and many other subjects, Wolfram|Alpha only requires Net access to use as much as you like, and I have made some serious use of it myself in noodling around with Calculus!
Desmos
This is an app you can download to your phone! This little gem makes it possible to do so many things offline, and is even more powerful when you use it with data or Wi-Fi. Awesome stuff!
Screenshot and equations by me. Interface and graphs by Desmos.
The Equation has its own limits...
but also has its unique strengths!
Wikipedia
All of the Math you could ever hope for! In multiple languages! Start in the shallow end, because the deep end is truly deep!
Mathplanet
"Study math for free!" Pretty much says it all, doesn't it?
Calculator Soup
"Online Calculator Resource". Just want the answer? Quickly find the answers here.
Your Public Library
Great resources for independent study, at your own pace, and with the ability to craft the material to fit in any nice little spot among your own Experiential Worlds!