The Extensible Computational Chemistry Environment (ECCE) provides a sophisiticated graphical user interface, scientific visualization tools, and the underlying data management framework enabling scientists to efficiently set up calculations and store, retrieve, and analyze the rapidly growing volumes of data produced by computational chemistry studies. Features include: Building complex molecular models including bimolecules importing Protein Data Bank (PDB) format files and periodic systems importing crystallographic (CAR) files; Graphical user interface to a broad range of electornic structure theory types. Supported codescurrently include NWChem, GAMESS-UK, Gaussian03 TM, Gaussian 98 TM, and Amica. Other codes can be added through the provided code registration mechanism without modifying core ECCE applications. Graphical user interface for basis set selection. Setting, Running, and visualizing results from NWChem Planewave Density Functional Theory calculations. Setting up, running and visualizing results from NWChem Molecular Dynamics somulations. Setting up, running, and visualizing results from NWChem Direct Dynamics Variational Transition State Theory (DirDyVTST) and POLYRATE gas phase reaction rate calculations. Building and executing task workflows pipelining data between chained and branched sequences of tasks for molecular dynamics and reaction rate calculations. Remote submission of calculations to UNIX and Linux workstations, clusters, and supercomputers. Supported batch queue schedulers include OpenPBS TM, LSF TM, SGET TM, LoadLeveler TM and Maui Scheuler. Support for other batch queue schedulers can be added through the provided compute servedr registration mechanism without modifying core ECCE applications. Lightweight job launching and monitoring capability using industry standard secure shell (ssh) for remote communications and no software installation or administration required on compute servers. Three-dimensional visualization and graphical display of molecular data properties while jobs are runing and after completion. Molecular orbitals and vibrational frequencies are among the properties displayed. Support for importing results from NWChem, Gaussian 94TM, Gaussian 98TM, and Gaussian 03TM calculations run outside of the ECCE environment. Extensive web-based help The ECCE application software runs on Linux workstations and is written in C++ using the wxWidgers user interface toolkit and OpenGL graphics.