The ILF System - A Tool for the Integration of Logical Functions. ILF is a shell that facilitates the work with a variety of theorem provers. Currently, it has interfaces with the automated provers Discount, Protein, Setheo and Spass.

SwitchMin Digital Circuit Minimizer - Tool for minimizing boolean logic functions.

The leanTAP Home Page - Lean, Tableau-based Deduction (theorem prover for first order logic).

SAT Hard Instance Generator and Solution Algorithms - Utilities and algorithms by V. Z. Nuri.

PROTEIN - A PROver with a Theory Extension INterface. Theorem prover for first-order clause logic, written in ECRC's Prolog-dialect ECLiPSe. Free download, documentation.

Theorem Provers - A list of (well-known) theorem provers on logic-server at the university of Muenchen. Good point to start.

3TAP - Many-valued tableau-based theorem prover developed at the University of Karlsruhe. It can be instantiated for arbitrary finitely-valued first-order logics, and it can handle equality (two-valued), sorts, and non-clausal input.

Bertrand - First-order satisfiability checker and prover for the Macintosh.

Database of Existing Mechanized Reasoning Systems - A list (>50 entries) of automatic resolution provers (like Otter), interactive provers (like PVS) and other mechanized reasoning tools.

Excel Logic Tool - Free Excel logic processor add-in for symbolic logic and mathematics.

Automated Reasoning Project - Web resource provided by research group. Includes access to software developed by the team, coverering such projects as FINDER (Finite Domain Enumerator), MaGIC (Matrix Generator for Implication Connectives) and Kripke (A theorem prover for the relevant logic LR).

MUltseq - A generic sequent prover for propositional finitely-valued logics.

MUltlog - Takes as input the specification of a finitely-valued first-order logic and produces a sequent calculus, a natural deduction system, and clause formation rules for this logic.

Isabelle - "The" Isabelle theorem proving environment.

WinKE: A Proof Assistant for Teaching Logic - WinKE is an interactive proof assistant based on analytic tableaux, and designed for the teaching of deductive reasoning. Ordering information is available at this site, as are academic papers on the design of the software.

The Coq Project - Deals with effectively machine-checked formal mathematics. In practice, this includes the study of mathematical formalisms well-suited for implementations, the implementations themselves and the use of these for various applications. Focuses on software correctness proofs.

ProofGeneral - Comprehensive Gnu-Emacs and XEmacs interface for several theorem provers (currently, Coq, Isabelle, Lego, and Phox).

Visual Turing - A graphical IDE that used to edit and play with Turing machines. Windows 95/98/NT/2000. Free to download, pay for source kit.

Logic Software from CSLI - By Jon Barwise and John Etchemendy.

ProofPower - A suite of tools supporting specification and proof in Higher Order Logic (HOL) and in Z notation.

LOOM - A language and environment for constructing intelligent applications. It is a research project in the Artificial Intelligence research group at the University of Southern California's Information Sciences Institute. The goal of the project is to develop and field advanced tools for knowledge representation and reasoning in Artificial Intelligence.

PROLIX - A logic programming language that has a syntax like that of PROLOG but that processes the sets of clauses in a way that is different and complementary to PROLOG. PROLIX will be able to solve questions that PROLOG will not, and viceversa. Requires Perl5 and MySQL.