C#

Chatter - Windows Forms IRC client. Uses NetIRC2 and SecondLanguage.
CryptSharp - BCrypt, DES Crypt, MD5 Crypt, SHA Crypt, PHPass, Blowfish, SCrypt, and PBKDF2 for any HMAC.
ENet for C# - ENet wrapper for C#.
HIDSharp - Multiplatform library for USB HID devices (COM enabled - also works in VB6 and MS Access).
Illusory Patcher Client - Software update library. Easy to integrate.
Illusory Registration API - Captcha generator, Base32 encoding, and name visual-similarity helper.
Japanese/Kanji Dictionary - JMDICT/KANJIDIC2 parser and Windows Forms Kanji control.
MySettings - Entirely .NET-native INI file reader/writer.
NBit - CRC calculator.
NetIRC2 - IRC client and Ident server library.
PODcaster - Byte-level struct conversion without unsafe code.
RemoteViewing - A .NET-native VNC client library. Includes a Windows Forms control for easy embedding.
SecondLanguage - Gettext translations on .NET, no hassle.
TrueTypeSharp - Tiny TrueType font renderer.
Voting Systems - Approval, Borda, Condorcet, Instant Runoff, and Plurality voting classes.
WPF: The Lost Controls - Controls WPF should but does not have.

Microsoft Access

Kanji Study Booklet Maker - Simple Microsoft Access template for making Kanji study booklets.