An Introduction to Quantum Mechanics
http://www.chemistry.ohio-state.edu/betha/qm
This site includes tutorials on probability, particles vs. waves, wave functions and more.
Uses Shockwave.

Quantum Mechanics Tutorial
http://www.gilestv.com/tutorials/quantum.html
This cool tutorial is one of the Flash-animated Modern Physics Tutorials by Giles Hogben.
Extensively illustrated, this tutorial probes questions such as wave-particle duality and offers a good general introduction to quantum physics.

Grains of Mystique:  Quantum Physics for the Layman
http://www.faqs.org/docs/qp
This site provides good historical and experimental background info - and they've documented their sources and made some attempts at peer review.

Quantum Physics Online Version 2.0
http://www.quantum-physics.polytechnique.fr/index.html
This is a cool set of programs that run in your browser, giving simulations of various quantum physics experiments.
Look for info on wave mechanics, quantization, quantum superposition, and spin 1/2.

Todd K. Timberlake's Tutorial
http://facultyweb.berry.edu/ttimberlake/qchaos/qm.html
A brief, but well-written, intro to the ideas of quantum mechanics.

Physics 24/7 Tutorial
http://www.physics247.com/physics-tutorial/quantum-physics-billiards.shtml
Includes material on quanta, the uncertainty principle, and quantum tunneling
(beware of ads)

Stan Zochowski's PDF tutorials
http://www.cmmp.ucl.ac.uk/~swz/courses/SM355/SM355.html
From the University College London.

Quantum Atom Tutorial
http://www.colorado.edu/physics/2000/quantumzone/index.html
A fun, cartoon-centric tutorial on the quantum nature of the atom from the 2000 UC Physics Project

College of St. Benedict's Tutorial
http://www.physics.csbsju.edu/QM/Index.html
A more serious text and equations-based tutorial with plenty of illustrations.

A Web-Based Quantum Mechanics Course
http://electron6.phys.utk.edu/qm1/Modules.htm
Extensive.   Includes modules on square potentials, harmonic oscillators, angular momentum, spin, etc.