From ictgames.com. Randomly type in all the words you need for a sentence substitution activity (even though the screen asks for a sentence). When you press the blue button it provides you with each word on a separate card. You can click and then pull these onto the runway to read as a sentence. Press the 'again' button to return the words to their starting places and make a different sentence. Useful for the 'apply' part of the lesson as a tool for the sentence substitution activity, but using your own sentences.
Alternatively, put in different phonetically plausible spellings of one of the words eg play, plai, pla, so the children have to select the spelling with the correct representation to put into the sentence.
Another variation is to put in the words to make a sentence containing a root word eg 'I hop in the park', but also add in additional words to change the sentence to contain a suffix eg 'I am hopping in the park'. Also include some incorrect spellings of the word with the suffix, so the children can apply the rules they've learnt eg 'hoping'.