Here's a good, quick read. It got its start about 10 years ago:
http://www.w3.org/DesignIssues/Principles.html
Topics:
- Simplicity
- Modular Design
- Tolerance ("Be liberal in what you require but conservative in what you do")
- Decentralization
- Test of Independent Invention ("If someone else had already invented your system, would theirs work with yours?")
- Principle of Least Power
When you're heads-down doing Agile or OOP sometimes you find yourself accidentally assuming that certain useful general principles are special to what you practice - when the truth is they're probably not even unique to your discipline, and some Greeks wrote them down around 500 BC.