Now this is an amazing site - Spelling City. Here you'll be able to access over 30,000 spelling words, including plurals, contractions, Dolch words and tricky words. There are several games students can play using these word lists.
I was surprised when I put in my own list of words then had the site 'test me.' It pronouced my words (in a human voice) and used my words in a sentence! So there you go! You can add your own spelling lists, have your students play a version of hangman (hang mouse) and other games with your lists. You can login to the site and create lists over literature books, science vocabulary, or whatever you want. Then your students can search for your list and play the games with those words. They can even take a spelling test with the computer pronouncing the word for them. This is a great tool for some independent and differentiated spelling activities.