Good spellers often recognise the shapes of words and one way to help weaker spellers is to encourage them to see these shapes too. For more on this see my posting: http://thespellingblog.blogspot.com/2009/01/seeing-spelling.html
I create worksheets for some of my spelling students with the outlines of words that they match with the words themselves. It takes ages in Word, fiddling about with tables and shading. So I was really pleased to find this: http://tools.atozteacherstuff.com/word-shapes/wordshapes.html You just type in the words and out pops a worksheet.
Here's one I made in less than a minute about words with 'p' and 'b', especially for my Arabic learners.
Also useful for confusing word endings such as 'el', 'al' and 'le'
( http://thespellingblog.blogspot.com/2009/02/spelling-words-ending-with-le-el-and-al.html )
What do you think? Useful?