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.
soupier soapier soppier super spier supper soaper seepier sappier spear spire supra spiry speer speir sopor sapour spirea sapper sipper zippier spiraea zappier spur spry spar sapphire spree spore sapor spoor spare spray sprue sparry spurry zapper zipper spurrey
roupier soupier pier pappier goopier pipier peppier loopier loppier mopier nappier rapier piper ropier super zappier dippier duper tippier upper whippier choppier lippier quippier sappier soppier hippier gappier pauper nippier cuppier cupper copier hoppier soapier seepier happier spier supper zippier dopier dupery typier weepier chippier yauper per