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.
spare spar spore spear spire spree sprue spirea sparry spiraea spry spur spurrey sparrow sapphire spray spoor speer spiry sopor speir spier sapor super supra sapper sapour sipper soaper spurry supper sappier seepier soapier soppier soupier
pare spare par pore spree pere spire rapparee pear guipure appear pyre pure prey pree pareo parr parae para pair coappear kouprey reappear spar pareu repair spear spore sprue