A generic sequent prover for propositional finitely-valued logics.
http://www.logic.at/multseq/
logic description language and simulator
http://www.cs.uiowa.edu/~jones/logicsim/
A tool that processes first-order logic problems and tries to find finite-domain models for them; written by Koen Claessen and Niklas Sörensson. Haskell and C++; free download under GPL.
http://www.cs.chalmers.se/~koen/paradox/
PCISIM is both a logic simulation library and a PCI simulation environment coded using the simulation library.
http://www.geocities.com/SiliconValley/Campus/3216/pcisim/pcisim.html
A list (>50 entries) of automatic resolution provers (like Otter), interactive provers (like PVS) and other mechanized reasoning tools.
http://www-formal.stanford.edu/clt/ARS/systems.html
A forward-chaining reasoning engine for defeasible logic, a less expressive but more efficient nonmonotonic logic.
http://www.dfki.uni-kl.de/~miller/delores/
development package that offers complete support for ICT's family of PEEL (Programmable Electronically Erasable Logic) Arrays and Devices
http://www.ictpld.com/
Mixed-signal analog and logic simulation software
http://www.dolphin.fr/medal/smash/smash_overview.html