Just found VocabAhead, a cool vocabulary practice site. It shows short videos for each word, and displays the words being spoken on screen as well. You can apparently embed the player, although it's not working for me in this post, or share out "your" word lists to your class. There are online quizzes and several other nice features, such as being able to peruse and use other people's word lists.
In the Study Room are predefined lists of 6th-11th grade words, a Master List, and 300 SAT words as well. You don't have to log on to use the predefined lists, always a nice thing.
There are lots of Google Play (Android) apps, and, via iTunes, a bunch of iPhone apps and 3 iPad apps. These include GRE, Spanish, Word a Day, Grade-level specific and many other vocab practice choices. A decent set of apps were free. Also had some choices in the Amazon store - worth looking there as well depending upon your platform...
CC Connection: This flexible, high quality site supports Reading Anchor Standard Craft and Structure # 4 Interpret words and phrases as they are used in a text....and analyze how specific word choices shape meaning or tone. It also supports Writing Anchor Standard Text Type and Purposes # 2 Write informative/explanatory texts to examine and convey complex ideas and information clearly and accurately through the effective selection, organization, and analysis of content, and #3 Write narratives to develop real or imagined experiences or events using effective technique, well-chosen details, and well-structured event sequences.