The University of Arizona's UACBT service (Computer-Based Training) offers 24/7 availability of FREE online training to over 1000+ courses and 98,000+ video tutorials, covering a broad range of topics and applications. See Tutorial Categories.
Most tutorials have between five and fifteen hours of content. Each tutorial is divided into lessons from 2-10 minutes long on average. Each lesson is available as a Flash, QuickTime, Adobe Air, or Adobe Air for Linux movie. You can stop, start, rewind, and review each lesson as often as desired.