Janis' ESL HomePage
This is a great site for very low levels. The site is organized by topics, such as "Jobs" or "Clothing". When you click on each topic, you are taken to about twenty more links, some of which are vocabulary review/pronunciation sites, some are vocab. quizzes, and a few are listening. It is quite good for having students review vocabulary covered in class.
ESL Flash Cards
There are tons of basic vocabulary and holiday flashcards that are free to print. Great for beginner vocabulary and grammar games.
This is a beginner visual vocabulary guide. You choose the topic (i.e. fruits), and picturers pop up. You listen to the pronunciation as you roll over the word. Great for beginners.
Henry Resource page
This site is out of France, but has the most wonderful set of links arranged alphabetically by topic. Each topic has links from a wide variety of sources from powerpoints to videos to handouts.
More Advanced Levels:
Academic Word List
If you are familiar with the 1000 most common academic word list, then you'll appreciate this site which breaks it down into 10 sublists, each with 6 groups and three online quizzes or each group. Very helpful with advanced reading and vocabulary classes.
Nice site with General Service List plus the Academic Word List as well as general academic words with building and practice activities
This is a very different kind of dictionary; it is online and graphical, showing words with similar roots and their parts of speech. It is better for advanced Students.
Forming different parts of speech from word bases
Extensive advanced chart with concept nouns, personal nouns, verbs and adjectives
Free for learners. Vocab trainer and personalized reports