AClock is an analog clock with display of smooth seconds. It stays in the dock. The display is customizable:

MPICH is a high-performance and widely portable implementation of the MPI-4.1 standard from the Argonne National Laboratory. It efficiently supports different computation and communication platforms including commodity clusters, SMPs, massively parallel systems, and high-speed networks. This release has all MPI 4.1 functions and features required by the standard with the exception of support for the "external32" portable I/O format and user-defined data representations for I/O.

JavaFX/OpenJFX is a set of graphics and media APIs that enables Java developers to design, create, test, debug, and deploy rich client applications that operate consistently across diverse platforms.

This program allows you to dump the traffic on a network. tcpdump is able to examine IPv4, ICMPv4, IPv6, ICMPv6, UDP, TCP, SNMP, AFS BGP, RIP, PIM, DVMRP, IGMP, SMB, OSPF, NFS and many other packet types.

Artikulate is a language learning application that helps improving pronunciation skills for various languages. This is included in the KDE Education project.