Op Amp Building Blocks
Here are two PDF files from the National Semiconductor Web Site that contain good tutorials on the fundamentals of Op Amp circuits and some of the basic analog building blocks that they can provide. The first document was written by the guru of Operational Amplifiers Robert Widlar in 1968 while the 2nd one, written in 1969 is somewhat derivative. These documents are excellent for the beginner as well good refreshers for more experienced engineers.
Op Amp Building Blocks diagrams, documents, and schematics: