Connection tracking userspace tools
http://conntrack-tools.netfilter.org

programming interface (API) to the in-kernel connection tracking state table
http://www.netfilter.org/projects/libnetfilter_conntrack/

low-level library for netfilter related kernel/userspace communication
http://www.netfilter.org/projects/libnfnetlink/

Collection of user space tools for general SMBus access and hardware monitoring
http://www.lm-sensors.org/

mdadm needs it to build

Scripts to set up quality of service with iproute2

System Utilities Based on Sysfs
http://linux-diag.sourceforge.net/Sysfsutils.html