libircclient is a small but powerful library, which implements client-server IRC protocol. It has all features needed to create your own IRC client or bot, including multi-threading support, sync and async interfaces, CTCP/DCC support, colors, SSL connections and so on.
A new kernel I am developing in my spare time. The eventual solution I hope will involve a 32 bit base kernel and 64 bit extensions therefore maximising compatibility with non 64 bit machines. Database oriented. Checkout http://www.love2code.org
UPDATE 18-Dec-2011
Updates haven't occurred for some time (April) due to working and studying for my Computer Science degree at the University of Ulster, but it's Christmas! so may be we'll get a little closer to doing some more work.
I have...
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Minirighi is a multi-threading open-source operating system written for didactic purpose. It has been written from scratch and it is compatible with POSIX.
Parallel Events and Asynchronous tasKing Library. Originally combining multi-threading with an efficient I/O event model, it's now more a lightweight object-oriented framework for event-based applications.
OpenTop is a cross-platform, high-performance C++ class library providing features similar to (and modelled on) core Java facilities such as resource management, networking, multi-threading, Unicode and XML parsing.