"If you want to build a ship, don't drum up people to collect wood and don't assign them tasks and work,

but rather teach them to long for the endless immensity of the sea." (Antoine de Saint Exupéry)

My favorite wikis on everything Web 2.0.

Cool Tools For Schools - By far the neatest and most helpful wiki with items organized in lists

New Tools Workshop - Another impressive work on Web 2.0 tools

Digital Teaching Tools - Spreadsheets with Web 2.0 tools you can use (description given as well)

PBS Indispensable Tools for Teachers - An A to Z list of tools

Web Apps for Educators - Neat lists (subject-related as well)

Karen Bolotin (@kbkonnected on Twitter) has done an amazing job curating everything Web 2.0 in livebinders here.

PB Works - Digitally Speaking (excellent resources for any educator: blogging, podcasting, social bookmarking etc)

EdTech Toolbox: Web 2.0 Tools by Task

Technology Tools for Teachers - organized by learning goal