testicle is a C++ unit test framework, choosing simplicity and flexibility before purism and framework-ishness. Its primary aim is to make it easy for lazy users to add a test: easy to understand how to do it, with no header file to keep in sync, and no need to somehow register each test (with the risk of forgetting to do it, and believing the test passes when in fact it never gets executed).
tinydyndns is a simple but powerful dynamic DNS solution that uses djbdns. It cooperates with the djbdns package to publish dynamic IP addresses authenticated through POP connections. On successfully authenticated POP connections, the tinydyndns-update program manipulates tinydns' constant database "data.cdb" directly without rebuilding it; this makes the dynamic DNS solution use very few system resources. Using a POP service for authentication saves the work for installing special client software, since POP clients are available for every common network-aware operating system. To provide the DNS and POP service, tinydyndns cooperates with djbdns, qmail, and cvm.
tmphoto is a Web photo gallery with a fairly advanced metadata structure, allowing photos to be described in terms of place, category, persons in the photo, and events. The places, categories, persons, and events can be further described. It offers a nice browsing interface based on the metadata.
Tomkitty is a Web server written in Java. It was conceived initially as a container for Web applications called Turdlets, themselves conceived as a simple alternative to Servlets. The code, though badly documented, has been put together with simplicity and understandability in mind and uses interfaces extensively. The general idea is a clean, stable, and scalable Web server in Java without the complexity and steep learning curve that comes with running the whole Tomcat system.