Note: Consider visiting Meg Ormiston's blog for a wealth of resources. She's by far one of the most enjoyable presenters I have had the pleasure of learning from at years of Tri-County Institutes.
Note: If you like Spell with Flickr, try The Visual Dictionary. Instead of searching for letters, it searches for entire words. As of January 2011, The Visual Dictionary boasts 7500 images of over 4000 words.