TYPO3*Cool Site* - Offers the official TYPO3 documentation, tutorials, the extension repository with downloads, organisation of the developer teams and a community with mailing list and a blog.
Cast Iron Coding Ressources - Offers a code collection with advanced knowledge about different aspects of TYPO3 programming, a forum and a link collection of tutorials for beginners.
CoolUri Tutorial - An extension for the static simulation of paths in the url of generated pages. Explains the installation, configuration and migration from realURL or Simulate Static to CoolUri.
Rggooglemap - All information about the Google Maps extension: Screenshots, examples, FAQ and information of the newest versions of the extension.
T3node.com - Blog with news and comments on the content-management-system and other web related issues.
TS Config Reference - Documentation for the usage of TypoScript Config. This is either used on pages to configure the backend for sub trees of the page tree or used on the backend users profile to individualize the backend.
TYPO3 Association - Website of the non-profit organisation organising the development of the content management system. Background information, how to become a member, and activity reports.
TYPO3 Board - English speaking support forum for TYPO3 programmers. Offers also downloads of helpful resources like documentation, installers and templates.
TYPO3 Documentation 4.0 - Official API of the TYPO3 source code listing files, classes and packages.
TYPO3 media - The Weblog from contains articles related to TYPO3 and its community.
TYPO3 Unleashed - Blog presenting news on TYPO3 and related web topics, several tutorials and a copy of the official API.
TYPO3 Wiki Resource - Great parts of the main TYPO3 documentation can be found in this Wiki ranging from helpful knowledge for beginners to advanced knowledge for extension programmers.
typo3bloke.net - Blog of Dmitry Dulepov, author of the book "TYPO3 Extension Programming". News on the community and tipps and tricks about coding.
typo3.com - The official website organized by the TYPO3 Association offers general information on the CMS and a list of reference projects.