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.
peppery pepper peppier papery peeper popery popper pappier paper piper pauper pipier papyri puparia
foppery coppery peppery lopper hipper quippier hoppier hepper nappier nippier napery coopery mapper hippier pepper lipper dapper copper hopper zapper gipper kipper dippier cuppier shopper tippier choppier chippier zipper whopper whipper upper popery papery rapper ripper wrapper sappier peppier soppier tapper mopper gypper happier loppier zappier perry lippier dipper lapper peery apery napper capper mopery nipper pappier paper knapper cupper quipper japery coappear dupery gappier popper tipper supper piper sipper sapper ropery reappear appear whapper bopper whippier chipper zippier chopper shipper topper yapper per pry