mbootpack is a tool that takes a Multiboot kernel and modules (e.g. a Xen VMM or a xen-linux kernel and initrd), and packages them up as a single file that looks like a bzImage Linux kernel. The aim is to allow you to boot Multiboot kernels (specifically, Xen) using bootloaders that don't support the Multiboot standard (i.e. pretty much anything except GRUB).
Hotplug lets you plug in new devices and use them immediately. That means that users won't need to learn so much system administration, since the Linux system will at least partially autoconfigure itself. Initially, hotplug included support for USB and PCI (Cardbus) devices, and could automatically configure some common network interfaces. Updated versions include IEEE 1394 (Firewire/i.Link) support and can download firmware to USB devices that need it.
openSSI webView is a simple and easy-to-use openSSI cluster monitoring system. Its goal is to provide a quick overview of the cluster state by graphing vital functions and graphically representing key figures. It allows the cluster administrator to keep an eye on the cluster health and usage rate, to quickly view each node state and load, and to watch, and even migrate, users' processes all across the cluster.
dstat is a versatile replacement for vmstat, iostat, netstat, nfsstat, and ifstat. It includes various counters (in separate plugins) and allows you to select and view all of your system resources instantly; you can, for example, compare disk usage in combination with interrupts from your IDE controller, or compare the network bandwidth numbers directly with the disk throughput (in the same interval).
ABISS (Active Block I/O Scheduling System) is an extension for the Linux kernel that implements priorities for disk IO operations, and that provides a means for applications to use these priorities to obtain real-time (e.g. a guaranteed data rate) and prioritized best-effort services. The kernel code is supported by a user space daemon and a library.
DragonFly belongs to the same class of operating systems as other BSD-derived systems and Linux. It is based on the same Unix ideals and APIs and shares ancestor code with other BSD operating systems. DragonFly is differentiated from other operating systems in its class by, among others, the HAMMER file system, Virtual Kernels, swapcache, and the pervasive use of soft token locks. DragonFly provides an opportunity for the BSD base to grow in an entirely different direction from the ones taken in the FreeBSD, NetBSD, and OpenBSD series.
v9fs provides a Plan 9 9P2000 resource sharing protocol for the Linux 2.6 kernel. This can be used to share files, devices, /proc, /sys, etc. It also works with Plan 9 file servers, and can be used to mount synthetic file systems from Plan 9 applications (see the plan9port project).