HEBCI is a technique that allows a Web form handler to transparently detect the character set with which its data was encoded. By using carefully-chosen character references, the browser's encoding can be inferred. Thus, it is possible to guarantee that data is in a standard encoding without relying on (often unreliable) Web server/browser encoding interactions.
libpuz is a C library implementing the .PUZ crossword file format. It allows users to read binary and text PUZ files and create binary PUZ files openable by Across Lite and other crossword programs. Also included is a (mostly) complete specification of the file format and checksum routines, in case you want to implement PUZ in a language other than C.
oscremoted is a daemon that listens for OSC events and runs commands in response to them. This allows you to build really general remote controls for Unix-like machines. OSC is an open standard for controlling audio equipment (similar to MIDI over the network). Tools exist to make arbitrary OSC GUIs to send button press events over the network.
index.rb is a general indexing framework for Ruby. With it, you can create collections of documents, then index and search them. The traditional inverted index is supported, as is Latent Semantic Indexing (LSI). Input documents may be stemmed, to make user queries more general. It also provides TextTiling to break input documents covering multiple topics into topic-specific sub-documents.