I've taken a list of English words, and examined each of them to see what they sound like (using the PHP metaphone function). This page lists the most common metaphone codes, along with their words. You can also search for a word of your own, and see which words sound similar - and which ones rhyme, and which ones alliterate.
spoor sapor sopor spore sapour spur spar spry speir spier spree sprue spiry spire spray spare supra spear super speer spirea supper sapper soaper sparry spurry sipper seepier soapier soppier soupier spurrey sparrow sappier spiraea sapphire
poor spoor poori pore pour vapor vapory vapour repour sapor sapour sopor spore