Here’s a handful of sites that have some useful free online tutorials & resources:
WolframAlpha – type in a question … get some pretty neat answers (tutorial here)
W3Schools – A generous and thorough coverage of web technology and it’s underpinnings; a great reference for many languages and architectures.
Lynda.com – Even non-subscribers have a wealth of useful and informative videos; the courseware is excellent.
Khan Academy – A plethora of free online classes from Algebra to Biology to Physics and much more
MacProVideo – Audio, Graphics and Video tutorials
Woopid – More useful tutorials
Wikipedia (how could we forget wikipedia!)