Here are some pretty cool online games to help people learn individual spellings:
Spelling City: http://www.spellingcity.com/ Type in some words that you have trouble spelling. Make sure you get the spelling right, but the program will tell you if it doesn't recognise a word. Then it speaks the word and also puts it in a sentence for you. How clever is that! Then it teaches you the spellings: you can play a variety of games with the words or it will test you.
East of the Web: http://www.eastoftheweb.com/games/index.html has got some very addictive games for people who like playing with words.