WebElements - [Very comprehensive, includes very detailed write ups, basic nuclide data, extensive graphics] Professional scientists and students at school will all find something useful. Includes thousands of images relating to periodicity and structure.

A Periodic Table of the Elements at Los Alamos National Laboratory - [Very basic data, detailed write-ups] The Chemical Science and Technology division's Periodic Table describes the history, properties, resources, uses, isotopes, forms, costs, and other information for each element.

Elementymology and Elements Multidictionary - [Very basic data] Explains the origins of the names of the chemical elements and lists element names in scores of languages.

Periodic Table of Elements - [Basic data] Chemistrydata.com offers very basic information about elements in a searchable format.

PTE Periodic Table of the Elements - [Very basic data, includes writeups, Requires Javascript]

Visual Elements - [Detailed data, write-ups, basic listing of nuclides] The Royal Society of Chemistry's (in the UK) contribution to chemistry on the web.

X-Ray Properties of the Elements - [X-ray properties only] X-ray properties of most of the elements.

The Periodic Table of Elements - [Detailed data, no write-ups] A Think Quest project

Exploring the Table of Isotopes - [Nuclide data only, extensive listing of nuclides] Provides isotope data for almost all known nuclides. From Berkeley Laboratory.

ChemicalElements.com: Online Periodic Table - [Basic data, limited write-ups] Provides information on the 109 named elements plus elements 110 - 112.

The Periodic Table Challenge - [No element data] An auto-scored blank periodic table. The user fills it in online and the score is returned automatically.

The Periodic Table of Elements by Kostas Tsigaridis - [Detailed data, basic nuclides, limited write-ups, requires Javascript] A Javascript based periodic table.

Periodic Table Matching Game - [No element data, requires Flash] An online learning activity for chemistry students. The goal is to drag element symbols onto their correct positions in the periodic table.

Printable Periodic Table - [Very basic data, requires Adobe Acrobat Reader] PDF of the Periodic Table arranged in different formats. Files only contain elements' symbols, names and atomic number.

EnvironmentalChemistry.com: Periodic Table of Elements - [Very comprehensive data, write-ups, extensive listing of nuclides] Data on elements includes scores of properties, element names in a dozen languages and almost all known nuclides. Environmental chemistry articles round out site.

The Extended Periodic Table of the Elements - [No element data] Displays and discusses three different extensions for the periodic table, regarding the issue of the placement of g-block elements.

Periodic Table of the Elements - [Very basic data] Includes printable version.

Colored Periodic Table and Chemical Bonding - [No element data] A colored periodic table which gives insight into the nature of chemical bonds, followed by a brief description of N. D. Epiotis's theory of T/I/E Bonding.

Periodic Table of the Elements - ChemGlobe - [Detailed data, includes write-ups, basic nuclide data, printable version] Chemical elements database from ChemGlobe.

Chemicool Periodic Table - [Detailed information on each element, no write-ups]

Table of the Nuclides - [Nuclide data only, very extensive listing of nuclides] Map of all known nuclides, with their atomic mass, radioactive decay modes and half-lives, and related information. Brookhaven National Laboratory.

Fast Periodic Table - Schoolscience - [Detailed data, basic write-ups, printable PDF version available. Requires JavaScript] This periodic table can generate bar graphs of some properties. The site also sells wallchart periodic tables.

The atomflowers of the Periodic Table. - [Basic data] Atomflowers growth when atoms are build up with their s, p, d and f orbitals according to the rules of the Periodic Table.

The Pictorial Periodic Table - [Basic data, very basic writeups, some pictures] Includes a printable periodic table, a cross-referenced list of nuclides, alternate styles, history, references, and many links to periodic table resources on the web.

On-line The Periodic Table of Elements - [Basic data, requires JavaScript] Includes historical information about the elements in Italian, but the table itself is in English.

Interactive Periodic Table and Data tables - [Very basic data, requires Javascript] Interactive table with pictures of the elements.

Periodic Table at resource-world.net - [Basic data, detailed nuclide info]

Chempros.com: Periodic Table of Elements - [Comprehensive data] Includes a brief historical overview of the periodic table.

Periodic Table of the Elements with Calculators - [Very basic data, requires JavaScript] Features a molecular mass calculator. Data includes spectroscopic terms and Xcore.

Periodic Table Quiz - [No data, quiz only - requires flash] Drag common elements to their correct positions within the periodic table.

David's Whizzy Periodic Table - Applet-based table with visualizations of the electron shell model, the nucleus, the visual emission spectrum, and energy levels of the electrons. Also has interesting facts about each element represented.

Printable Periodic Table - [Very basic data] Minimalist table that provides symbols, atomic numbers, and atomic weight with four significant figures.

Gordon England's Periodic Table of the Elements - [Detailed data]

Periodic-Table.org - [Very basic data] Includes alphabetical list of symbols and names, and detailed information about a few elements.

Periodic table of the elements - [Comprehensive data, write-ups, reduction potential tables] Includes interactive JavaScript calculators, glossary of chemical terms, and a printable PDF table.