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.
ropier roupier roper rapier ropery raper riper rapper reaper repair ripper wrapper reappear repour rapparee
happier loopier peppier zappier soapier hoppier seepier ropier typier dippier tippier sappier dopier pappier loppier zippier goopier gappier choppier chippier pier cuppier nappier spier copier whippier soupier quippier weepier pipier rapier roupier nippier hippier lippier soppier mopier per mapper paper hoper pear hopper lipper leaper pauper taper reaper sapper hyper aper tapir pere kipper reappear supper ropery popper lopper coppery gypper popery sipper hepper hooper upper leper yauper shopper shaper cheaper whopper wrapper whapper soaper toper dupery chipper mopery chopper beeper rapper speir riper lapper raper peri cupper gaper tapper piper hipper weeper roper zipper diapir dapper repair peppery loper copper foppery duper spear deeper coper napper diaper japer topper appear spire looper doper spiry opera coopery nipper knapper peeper super gawper peer caper napery moper apery gipper pair cooper japery capper coappear papery bopper speer quipper pepper ripper tipper keeper mopper zapper whipper whooper wiper cheeper viper dipper heaper shipper yapper yawper
rope ropey ropy roup roupy rupiah crop croppie grope prop drop trop trope