Software

AcerMC Monte Carlo Generator
The AcerMC Monte-Carlo event generator is dedicated for generation of the Standard Model background processes in pp collisions at the LHC.
http://borut.home.cern.ch/borut/

The CalcHEP and CompHEP Projects
Two Tools designed to calculate cross sections in high energy physics.
http://www.ifh.de/~pukhov/

CERN Computing Documentation
Provides CERNLIB documentation. Also provides tutorials, FAQs, newsletters and reference cards for a wide range of software.
http://consult.cern.ch/service/documentation/

cfortran.h - Interfacing C/C++ and FORTRAN
cfortran.h is a single header file that allows you to easily use fortran code in c and c++. Very useful for using HBOOK and other CERNLIB code in new c++ applications.
http://www-zeus.desy.de/~burow/cfortran/

Elementary Particles Simulation
Elementary Particles Simulation using Java Technology.An application made for educational purposes.
http://mikeathan.tripod.com

Fermitools
The Fermilab Software Tools Program (Fermitools) aims to provide useful tools to the community. A wide range of tools are available, and all are free.
http://fermitools.fnal.gov/

FeynArts
Mathematica package for generation and visualization of Feynman diagrams and amplitudes.
http://www.feynarts.de/

FeynCalc
Mathematica package for algebraic calculations in elementary particle physics, focusing on Feynman diagram calculations.
http://www.feyncalc.org/

FeynDiagram.com
Free C++ library for drawing Feynman diagrams. The output is in PostScript, which can be used in TeX or printed directly.
http://feyndiagram.com/

FeynFig
FeynFig is a program to generate feynman diagrams in xfig format.
http://www.lpthe.jussieu.fr/~salam/feynfig/

Feynmf
Drawing Feynman diagrams with LaTeX and Metafont.
http://xml.web.cern.ch/XML/textproc/feynmf.html

FLUKA (Fluktuierende Kaskade)
A stand-alone particle physics Monte-Carlo simulation package. It is being used as a simulation tool in a number of experiments.
http://www.fluka.org

Hanna
A C-based Analysis Tool for the HERMES experiment at the DESY laboratory in Hamburg, Germany.
http://hermes.desy.de/hanna/

HERWIG
A Monte Carlo package for simulating hadron emission reactions with interfering gluons. Also includes a list of some "competitor" generators.
http://hepwww.rl.ac.uk/theory/seymour/herwig/

JaxoDraw
A Java program for the interactive drawing of Feynman diagrams
http://altair.ific.uv.es/~JaxoDraw/

Monte Carlo Number Scheme
MC particle numbering convention, endorsed by the Particle Data Group.
http://pdg.lbl.gov/mc_particle_id_contents.html

Pandora
A physics event generator for linear collider studies. It includes beamstrahlung, initial state radiation, hadronization, and full treatment of polarization effects.
http://www-sldnt.slac.stanford.edu/nld/new/Docs/Generators/PANDORA.htm

Phi (Phenomenology of Hadronic Interactions)
Extension of the Mathematica packages, FeynCalc and FeynArts.
http://www.feyncalc.org/phi/

Povama
Persint OpenGL Visualization for ATLAS Muon Analysis. Software used to visualize the reconstruction of muon traces.
http://povama.sourceforge.net

PYTHIA (and JETSET)
An event generator for a large number of physics processes. The site contains the latest source, the official manual and a short write-up describing PYTHIA's status with respect to the physics.
http://www.thep.lu.se/~torbjorn/Pythia.html

The ROOT System
An object oriented framework for large scale data analysis. ROOT is a C++ replacement of the popular PAW program developed at CERN.
http://root.cern.ch/

StdHep
Provides a common output format for Monte Carlo events so that event generators and other simulators can easily be compared. It also provides a set of routines which convert Herwig, Jetset, Isajet, or QQ events to and from the standard HEP event format.
http://www-cpd.fnal.gov/psm/stdhep/

Texsis - TeX Macros for Physicists
This package provides a number of useful features for typesetting research papers. It is an extension to Plain Tex.
http://www.texsis.org/