C++
Common Code - Assorted useful classes.
C#
AsyncNet (beta) - Asynchronous network library. Made in the style of Twisted Python.
Chatter - Windows Forms IRC client. Uses NetIRC and NetIdent.
CryptSharp - Blowfish, BCrypt, SCrypt, and PBKDF2 for any HMAC.
ENet for C# - ENet wrapper for C#.
HIDSharp - Basic wrapper for HID and USB postal scales (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.
NetIRC and NetIdent - IRC client and Ident server library.
PODcaster - Byte-level struct conversion without unsafe code.
Voting Systems - Approval, Borda, Condorcet, Instant Runoff, and Plurality voting classes.
TrueTypeSharp - Tiny TrueType font renderer.
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.