Celeste  
   An interactive periodic table software product for Windows with graphing capabilities.
   http://www.chemlearn.com

BK Periodic Library  
   Windows periodic table with element properties search and graphing. Free for personal use.
   http://www.orbit.org/perlib/

Synergy Creations  
   Developers of general educational software for the Macintosh platform, including Periodic Table software. Online purchasing available.
   http://www.synergycreations.com/

PTViz: Periodic Table Illustrator  
   Macintosh freeware for the creation of periodic tables with selected properties for use in presentations. Each element is colored according to the value of the selected property.
   http://www.optc.com/PTViz.html

Atomic Mac  
   An electronic version of the periodic table of elements with detailed physical and nuclear information.
   http://www.blackcatsystems.com/software/atomic.html

Atomic PC  
   Downloadable Windows shareware containing abundant physical, chemical and nuclear information about the elements. Online registration available.
   http://www.engresource.com/software/atomic.html

Electronic Periodic Table of the Elements  
   Text-based periodic table for Unix. The source code, written in C, is available for download and use under the GNU GPL. It includes sound files that give element names and definitions out loud.
   http://www.toddmiller.com/epte/index.html

Periodic Spiral of the Elements  
   For Mac and PC, an alternative representation of the periodic table that aims to better place the lanthanoids, actinoids, and hydrogen. The program also includes extensive information about elements, their uses and their properties. Shockwave demo availab
   http://www.periodicspiral.com

ChemAP 2000  
   Chemistry software for the Windows environment.
   http://usuarios.lycos.es/chemap/

iChem: Periodic table for Mac OS X  
   iChem, written in Cocoa for Mac OS X exclusively, is a full-featured periodic table and molecular weight calculator.
   http://www.barzeski.com/ichem/

SeaSick Electronics  
   Periodic Table of the Elements.
   http://cesicelectronics.com/software.htm