DbDesigner is a useful tool for constructing databases in an intuitive and easy-to-use environment, where you have a visual representation of the tables and relations contained in your project. You can quickly see the fields in a table or how each table relates to the others. After you are finished, it can export the schema of the database into an .sql script, or directly connect to a database backend and build it there. It can also import already existing databases from .sql scripts or db backends. It can save your project into its native format (XML) so all information is kept, and it has a plugin architecture to be easily extensible to work with many database servers (it comes with 2 plugins for PostgreSQL and MySQL).
BIOS Writer allows you to copy the settings of your PC's BIOS to a small image file. You can then mess with the BIOS and later restore the previous working settings. One use would be to pull two settings files from a remote machine's BIOS -- one with network booting enabled, and one with hard disk booting enabled. You can then use BIOS Writer to tell the machine to boot off the network or its hard drive by restoring the appropriate settings file.
layout is a tcl package that allows you to create layouts simply and efficently. The layout you want is "written" in a variable that is parsed by proc "layout", which will arrange for normal managers (grid and pack) to handle it. Since the variable can be dynamically created, the layout can be created on the fly. The format of the variable is intuitive so that reading the code is easy, and change in the layout can be done in seconds. Comes with a detailed demo.
Citrus is a library for converting numbers with units into numbers with other units. It accomplishes this by performing dimensional analysis on the units. This allows input and output to be expressed in terms of many different units simultaneously, combined via multiplication, division, and exponentiation.
pingx is utility that uses the XNoOp(3x) call to see how fast your connection to your X server is. Wonder whether your X performance is slower in a SSH tunnel? pingx can give you hard numbers so you can find out. It has an option to print out some details about the X server as well. It's also useful to see if a destination X server is up so you can fire up x2x or similar applications intelligently.