http://www.sadlier-oxford.com/vocabulary/levels_a2h.cfm 

Vocabulary Builders Level B

Vocabulary Builders Level C

Vocabulary Builders Level D

Vocabulary Builders Level E 

 Dictionaries

• Merriam Webster

• Dictionary.com

• Google is also a dictionary! In the search box, type "define:" (without the quotes) and the word you are looking up.