An excellent economic analysis by Bruce Perens on how open source works. I think it is much more better than Raymond's famous and inspiring but not economically sound series, although Raymond is a hardcore libertarian. ;-)
ModelSecurity helps Ruby on Rails developers implement a security defense in depth by implementing access control within the data model.
The economical, flexible, and extremely readable means of specifying access controls provided by ModelSecurity makes it easier for the developer to think about security, and makes security assumptions that might otherwise live in one developers head concrete and communicable to others.
malloc() debugger written by Bruce Perens for Linux and Unix. This will stop your program on the exact instruction that overruns or under-runs a malloc() buffer.