Yacas is a general purpose, easy to use Computer Algebra System (a CAS is a program that can be used to do symbolic manipulation of mathematical expressions). It is built on top of its own programming language designed for this purpose, in which new algorithms can easily be implemented. In addition, it comes with extensive documentation on the functionality implemented and methods used to implement them.
ChBg is for changing desktop backgrounds in a given period. It can render images with 10 modes (such as tiled, centered, scaled, etc.). It uses Imlib1, Imlib2, or gdk_pixbuf for loading images, so it supports many image formats. ChBg has a windowed setup program, is able to load setup files, can be used as slideshow picture previewer in its own window or as a desktop background, and can be used as screensaver or as an xscreensaver hack. It has a dialog for fast previewing of pictures and very usable thumbnail previews.
Sticker Book is a children's program which lets you place stickers on a background scene. You can resize, recolour and reorient the stickers that you use, and you never run out. You can even paint with them. The program is intended for the 3-7 year olds, but it's even fun for adults. It is flexible enough to make sophisticated pictures without being as complex as drawing/painting program.
Hwclock is a program that runs under Linux and sets and queries the Hardware Clock, which is often called the Real Time Clock, RTC, or CMOS clock. This is the program that most Linux systems use to get the time from the Hardware Clock and set the System Time at boot time. This program works on ISA (Intel), Alpha, SPARC, and M68K systems with or without /dev/rtc.
The Extent File System (efs) is Silicon Graphics' early block-device filesystem, widely used on pre-6.0 versions of IRIX. Since 6.0, xfs has been bundled with IRIX and users are being encouraged to migrate to xfs filesystems. IRIX support for efs will be read-only in versions of IRIX beyond 6.5, however efs is still very much in use on SGI software distribution CDs.
tn5250 is a 5250 terminal emulator, used for connecting to IBM's AS/400 (now known as eServer iSeries) midrange computers. tn5250 implements TN5250E, which means it is capable of device name selection, and printer sessions. The emulator supports color, 132 column mode, and most other features found in 5250 terminals and Client Access' 5250 emulator. While tn5250 is text-based application, a script is included to run it in an xterm properly. If you don't know what an AS/400 is, this program will probably not be of much use to you.