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