The iotools package provides a set of simple command line tools that allow access to hardware device registers. Supported register interfaces include PCI, I/O, memory mapped I/O, SMBus, CPUID, and MSR. Also included are some utilities that allow for simple arithmetic, logical, and other operations. If you ever have to debug hardware, you could probably use these tools.
prettyprint is intended to provide an infrastructure and tools to describe and manipulate hardware registers and fields. Once described, it is possible to read and write fields symbolically. This allows one to browse the state of their hardware. Examples provided include simple state dumpers as well as a FUSE filesystem.
Ejecter is a little tool that makes it possible to unmount external devices and eject CD-ROMs without having to right-click on the device icon (either on the desktop or in Nautilus). It sits in the background and shows an icon in the system tray when one or more peripherals are connected to your PC: once clicked, a window appears with the list of the devices (volume name and device type, and much clearer than the similar thing available on Windows) and the related eject button. Being written in Vala, it is translated into C code and then compiled. This means that it's lightweight and consumes little memory, does not require a full VM like Python, and has no strange requirements to run (just GLib/GTK).
hwmultd is a daemon which, when run in server mode, periodically polls some hardware device, like an entropy source, and multicasts that information. Alternatively, hwmultd can run in client mode, listening for multicasted information and then acting accordingly, like adding gathered entropy to the local pool. Its simple plugin system allows hwmultd to be agnostic with respect to the hardware, which could include devices such as temperature probes or time sources.