If something can go wrong, it will.
Adding manpower to a later software project makes it later.
It always takes longer than you expect, even when you take into account Hofstadter's law.
Any piece of software reflects the organizational structure that produced it.
Be conservative in what you send, be liberal in what you accept.
For many phenomena, 80% of consequences stem from 20% of the causes.
The Peter Principle
In a hierarchy, every employee tends to rise to his level of incompetence.
Given enough eyeballs, all bugs are shallow.
The processing speed of computers will double every two years!
Software gets slower faster than hardware gets faster.
The first 90% of the code takes 10% of the time. The remaining 10% takes the other 90% of the time.
Knuth's Optimization Principle
Premature optimization is the root of all evil.
Any technology that surpasses 50% penetration will never double agin.