Theorem Proving
Isabelle - popular generic theorem proving environment, written in ML.Proof General - generic interface for proof assistants, based on Emacs.
TAS and IsaWin - tools for formal program development and theorem proving.
Coq - proof assistant written in Objective Caml.
Pcoq - a working environment for the Coq theorem prover.
CtCoq - ancestor of Pcoq.
Freek Wiedijk - lots of links to computer math systems.
-> The Fifteen Provers of the World - comparison of proof assistants.
Programming
Thinking in C++ - free electronic book.wxWindows - open source C++ GUI framework for cross-platform programming.
libxml - XML parser and toolkit developed as part of the Gnome project.
SRP - open source secure password-based authentication and key-exchange protocol.
libtinysrp - simplified SRP API.
netcat - TCP/IP Swiss Army Knife.