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.
hoppier hopper happier hippier hoper hepper hipper hooper heaper
hippier nippier soppier tippier whippier quippier sappier happier cuppier peppier lippier chippier dippier zippier nappier zappier loppier choppier hoppier pappier gappier pier hipper mopper pepper reappear supper mapper gipper capper rapper goopier sipper rapier hopper wrapper weepier tipper lopper shopper seepier typier whopper whipper coappear topper copper zapper zipper ropier copier pipier coppery knapper appear cupper gypper sapper loopier mopier foppery soupier kipper soapier hepper lipper nipper dapper spier bopper whapper tapper piper paper popper shipper chipper ripper quipper upper dopier roupier napper lapper dipper peppery chopper yapper per