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.
spore sopor sprue spare spree sapor spire spoor spirea sapour spry spurrey spiraea spur spar sapphire spray spiry speer spear spier super speir supra sparry soaper sipper sapper spurry supper sappier seepier soapier soppier soupier sparrow
pore spore spree spire prey spoor spare sapour pere poor pour pree sopor pure vapor pyre vapory vapour guipure kouprey repour sapor pare sprue