I've just come across a website that has a lot of good freshwater fishing information.
Learning How to Fish
I particularly recommend reading their "The Underwater World of Freshwater Fish" page for information on lake structure and water types, etc.
The website has good information on knot tying and fish characteristics. The places to fish and species specific information are a bit too limited to be of much use but the first few links along the left side provide some really good very basic freshwater fishing information.