If you would like to provide middle and high school students with a fun online site to build word awareness, why not have them enroll for free at ACADEMIC VOCABULARY.
In one section, the words are out of context (as they are on high stakes tests), but if students don't know the answer, they can click for help. The program keeps a record of points earned once student joins the site.
WORD LISTS can be found in English, social studies, historical documents, speeches, literature, and SAT words. If the words here don't quite meet their needs, students may build their own lists or ask their teachers for words to add.
Last, but not least, students may either share their lists on the site, or use submitted word lists from other users.
One more thing, teachers may have some fun here as well. I know I did:)
ELL TEACHER PROS