This is an interesting article about how to bypass PaX. It shows why other technologies are needed, such as SSP and various transparent grsecurity features, with a PaX kernel. Even more important, it demonstrates that we must continue to search for viable solutions to suppliment the security of all operating systems.
The original paper by the ProPolice authors. This paper goes as far as to explain the problem; to explain existing solutions; to compare existing solutions in terms of effectiveness, portability, and overhead; and to explain the limitations of the ProPolice protection method.
The home base of the PaX project.
The home base of the grsecurity project. This project adds many transparent and visible security enhancements to the kernel, including a full ACL system.
Hardened Gentoo is a subproject of Gentoo Linux which adds many security enhancements to Gentoo. The features originally used for this project were the features available in Hardened Gentoo which the original author of DSbD chose to use on his home systems.
Hardened Debian appeared at around the same times as D:SbD. The two projects have roughly the same end goals: to make Debian secure. These guys are working on a hardened Debian kernel as well, with various patches in it; D:SbD currently hosts their apt repository for mutual benefit.
A secured version of Debian, Adamantix contains technologies that are overkill on a home user's system (RSBAC), but that may hold great value on installations requiring a high level of security. DSbD aims to bring a subset of the features of Adamantix, such as PaX and SSP, to standard Debian GNU/Linux.