Software

Security & privacy related software

EasyPG
EasyPG is a GnuPG interface for Emacs. It provides automatic file encryption, keyring browser, etc. This software was merged into Emacs and you don't need to install it seperately.
Ruby-GPGME
Ruby-GPGME is a ruby interface to GnuPG Made Easy (GPGME), a library to use GnuPG from application programs. It now comes with a Ruby on Rails plugin.
Ruby-HMAC
Ruby-HMAC is a ruby implementation of RFC2104, "HMAC: Keyed-Hashing for Message Authentication". It is currently maintained by Geoffrey Grosenbach.

linenum→info
linenum→info is a Web-based collaboration tool supporting "code reading", a group work to proof-read the open-source code. It provides bird's-eye view of the source code, full-text search, collaborative editing of comments, etc.
treil
treil is a simple tool to draw Treemap, a technique to visualize hierarchical data. Since treil is designed to visualize the source code, the output diagram is colored by modification time if the input is version-controlled.
msgcab
msgcab is an easy-to-use mailing list archiver. It uses a novel algorithm for message threading to handle cross posts efficiently. It can be extended by plugins.

Emacs & XEmacs
Emacs is my current text editor of choice. I have been a developer of it since 2007. I'm the author of a bunch of security related libraries including SASL, STARTTLS, EasyPG, PGG, etc. and took charge of adopting those security features into other part of Emacs. Before I began to contribute to Emacs, XEmacs was my favorite text editor. I have been involved in the development since 2001.
GnuPG and related software & libraries
In GnuPG, I implemented a mechanism to cache passphrase for symmetric encryption using S2K salt as the cache key (it is included in the version 2.0.12). In GnuTLS, I implemented RFC5077 session ticket support (it is included in the version 2.9.3). I'm currently proposing RSA-OAEP padding support for Libgcrypt.

Ristet
Ristet is a remake of Tesrit, a Tetris-style game running on old MSX computers.
Roach
Roach is a Palm Pilot port of Xroach, a desktop accessory for X Window System.
Riece
Riece is a fully-featured IRC client for Emacs. It can be extended by add-ons, and currently 35+ add-ons are included.
LSDB
LSDB is a simple address book for Emacs MUA like Gnus, Wanderlust, Mew, etc.
sysvipc
sysvipc is a Ruby module for System V Inter-Process Communication: message queues, semaphores, and shared memory. It is currently maintained by Steven Jenkins.