The NTRU public-key cryptosystem provides a Java implementation of the NTRUEncrypt and NTRUSign algorithms. Both algorithms are considered safe against quantum computer attacks. A C port of NTRUEncrypt is available, as well.
TommyDS is a C library of hashtables and tries designed for high performance. It's faster than other similar libraries like rbtree, khash, goodledensehash, uthash, judy, nedtrie, and others.
libibuddy is a library to control the i-Buddy device in Unix. A command line tool called ibuddycmd is also included with the library to drive the i-Buddy from the command line or a script. libibuddy uses the libusb interface to communicate with the device.