There are countless websites that are useful to teachers. Here are a few I use.

TESOL - Teachers of English to Speakers of Other Languages. Here there are many useful resources and is a good start point for teachers to become part of an educational community.

Super Teacher Tools - Here you can find many tools that help during class. From classroom management to Jeopardy.

Wordle - This tool is very easy to use. In just a few clicks you can make word clouds that can be used in many different ways.

Visuwords - This is a great visual dictionary. I use it very often for brainstorming and vocabulary build-up.