Techniques for placing components on PCB's
Here are some of the links and documents I have saved over time:

Henry Ott's site - lots of good stuff here
Electromagnetic Compatibility Engineering - Henry Ott - the best book I have read on high speed layout and EMI issues.
PCB Design for Manufacture Blog (EEVBlog - David Jones)
Wikibooks - PCB layout
PCB Layout Checklist (from one PCB manufacturer, but useful general list)
High Speed Layout Guidelines - TI
High Speed Amplifier Techniques - Linear Tech AN47 - by the late great Jim Wiliiams
A Practical Guide to High Speed PCB Layout
Hardware Design Techniques - Chapter 9
Hardware Design Techniques - Section 9
Hardware Design Techniques - Section 10
Hardware Design Techniques - Section 7
Analog Dialog Archives
HP Journal Archives