Yet another great list from waterandstone.com, thus.. I really miss Jumi - an extension to add your own PHP code into articles.

With more than 4,000 Extensions in the Joomla! Extensions Directory, one of the most daunting aspects of selecting a Joomla! Extension is finding the right tool for the job. With thousands of Extensions to choose from, you are sometimes faced with multiple options that appear to achieve your goals. While there really is no subsitute for downloading things and trying them out yourself, in this article I provide a list of fifty Joomla! Extensions as a starting point for addressing common needs.

1. Automatically generated site sitemap (html & google xml sitemap) - Recommend XMap plug-in
2. Forum (integrated into Joomla, use the same user management system) - Recommended FireBoard Forum plug-in
3. Voting system - simple to use Joomla built-in vote Poll enough. The need for complex voting can use plug-in pollXT