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!
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!
You can use YouTube cautiously as a resource for information, and if you have something to share with others, this provides you with real possibilities in terms of video. I made a video myself, using tools listed below, a thumb drive, and the computing resources at the library! I'm hoping to upgrade my resources soon, but look at what can be done, even with the bare minimum!
PortableApps.com This is how to make your USB thumb drive into an on-the-go powerhouse of tools! Simply download and install the main program to your thumb drive, and then add any number of other programs to this platform, and take it with you in your pocket! Two of my favorites are Stellarium and Celestia, though you'll notice I have a few other tools, and games as well. P:D