I bought this full course some years ago and it was very good. It's some money and it's far from all you'll need to get a grip on everything, but it is a useful part of the learning process.

The product-

http://www.moultonlabs.com/full/product02/

To buy-

http://www.recordingmag.com/category/77.html

Now, the best way is to sit at a mixing board and/or at one of the many fine Daws out there and just dive in with simple projects. Twist dials, listen, twist some more. Learning what a dial on an eq or comp or limiter is just isn't enough. You have to twist said dials, make the audio sound like crap, and bring it back, to learn what all this stuff is and how it works. Hands on is often the best and cheapest way to get up to speed. Good luck.

Dan