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.
whipper whippier whapper whopper wiper whipray whooper weeper weepier
hipper shipper gipper kipper quipper sipper tipper whipper lipper dipper zipper chipper nipper ripper upper whapper cuppier popper coppery nappier zapper soppier peppery nippier sappier pappier knapper diaper choppier cupper mapper dapper sapper gypper lopper hopper topper whippier supper chippier coappear piper shopper zippier peppier paper loppier tapper hoppier hippier lapper lippier capper mopper rapper riper viper pepper copper gappier pipier wiper quippier happier foppery wrapper chopper whopper tippier appear hepper reappear napper bopper dippier zappier yapper per