twocrypt (2c) is a tool for the ultra-paranoid, providing a traditional crypto, but also an option of deniable (subpoena-proof) encryption. It encrypts one or two files at once. Each file can be recovered with its respective passphrase, but the presence of more than one file cannot be demonstrated, and the presence of this option alone should not be a credible argument for data hiding.
twonz is a small Perl/TK program which lets you generate and manage the endless quantities of passwords you may need to get anything done online. Rather than making an encrypted database or anything, it just calculates a secure hash of obvious information appended to a user-supplied pad. So you only have to remember the pad, and none of your passwords are actually stored anywhere at all.
txtorcon is a Twisted-based asynchronous Tor control protocol implementation. Twisted is an event-driven networking engine written in Python, and Tor is an onion-routing network designed to improve people’s privacy and security on the Internet. It includes unit-tests with 96%+ coverage, multiple examples, and documentation. There are abstractions to track Tor configuration and state (circuits, streams), launch private instances, support Hidden Service, and more.
ucspi-ipc implements D. J. Bernstein's UCSPI protocol in the Unix domain, making it trivial to set up clients or servers on Unix sockets. ucspi- ipc comes with utilities using credential passing on Unix sockets, which are designed to act like a fine-grained and efficient sudo without the need for setuid programs.
ulock locks the entire virtual console system, completely disabling all console access. It gives up these locks when either the password of the user who started ulock or the root password is typed. It is able to invoke any program (i.e. a screen saver), which will be terminated on any keystroke. The idea of the program was taken from Michael K. Johnson's vlock.