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