I thought it might be useful to collect a few application notes in one place that are not focused on a specific device, but explain a general topic or provide examples of it. Although it is inevitable that the example circuits will advertise the companies devices, such app notes are often more useful than university course notes because most of them explain stuff with a minimum of theory and mathematics.
I know there is a good thread about free learning resources in the Beginners forum, but most app notes are at the intermediate level and assume at least a basic knowledge of electronics, so I think this forum is better suited for them. I'll start with a few examples and hope that others will share their stuff.
High Speed TechniquesAN47 High Speed Amplifier Techniques (1991) by Williams
Not only about amplifiers, but also very good advice about the use of scope probes and other problems that are relevant for high speed circuits, lots of (analog) scope shots
http://cds.linear.com/docs/Application%20Note/an47fa.pdfOp Amp TutorialsOp Amps for Everyone (2002) by Mancini
Popular op amp tutorial, also good explanations of other topics like noise
http://focus.ti.com/lit/an/slod006b/slod006b.pdfOp Amp Applications (2002) by Jung
More advanced than Mancini, everything you ever wanted to know about op amps and much more
http://www.analog.com/library/analogdialogue/archives/39-05/Op_Amp_Applications.zipOp Amp Circuit CollectionsSBOA092A Handbook Of Operational Amplifier Applications, original by Brown (1963), completely updated by Carter (2001)
On page 48 starts a collection of (mostly simple) op amp circuits
http://focus.ti.com/lit/an/sboa092a/sboa092a.pdfAN-20 An Applications Guide for Op Amps (1968)
Old app note, but good explanations of the circuits
http://www.national.com/an/AN/AN-20.pdfAN-31 Op Amp Circuit Collection
87 op amp circuits but without explanations
http://www.national.com/an/AN/AN-31.pdfAN-106 A Collection Of Amp Applications by Wong
Collection of 38 advanced op amp circuits with explanations
http://www.analog.com/static/imported-files/application_notes/28080533AN106.pdfSLOA058 A Single Supply Op-Amp Circuit Collection by Carter
Collection of single supply op amp circuits, most of them filters
http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=sloa058&fileType=pdfSine Wave OscillatorsAN263 Sine Wave Generation Techniques (1999)
Good overview: Various sine oscillators, oscillators with triangle outputs that are then shaped to sine waves, digital methods.
http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=snoa665b&fileType=pdfSLOA060 Sine Wave Oscillator (2001) by Mancini and Palmer
Some oscillator theory and a discussion of Wien, phase shift, Bubba and quadrature sine oscillators
www.ti.com/lit/an/sloa060/sloa060.pdfAN43 Bridge Circuits (1990) by Williams
On page 29 starts a discussion of several Wien bridge oscillators with very low distortion
http://cds.linear.com/docs/Application%20Note/an43f.pdf