If there's one person you can always rely on for quality when it comes to literacy it's the Gandalf of Grammar himself Alan Peat.
(note to Alan - that's got to be my best nickname for you yet surely?)
Alan has now started releasing a string of free game apps that support the development of spelling for primary age students. The Spellfix apps are split into 30 progressively more challenging lists with 8 words to identify in each using the given bank of letters. For each word you are given a definition clue and you can also opt to show the first two letters of each if get stuck. As the game doesn't work on a time limit, students can use a dictionary or thesaurus if needed to locate the answer.
They're great fun and several titles are already available with more in the pipeline. The core app covers 240 commonly misspelt words but there are dedicated apps for key spelling patterns like double l words, -ck words, double s words and common digraphs like ai, ee and oi amongst others. There is even an app dedicated to the yr3-6 core spelling lists. Alan actually has FIFTY of these apps set for launch so everything possible really will be covered!