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.
coppra copra copperah copper coprah coppery coper coappear copier cooper capper cupper coopery cuppier capoeira caper kipper gappier goopier kouprey quipper quippier
coppra hipper gypper gipper capper ripper spray sapper supra opera popper napper dipper mopper zipper tipper lopper upper kipper whipper lapper whopper copra chopper copper shopper coprah hopper hepper dapper cupper proa bopper pray wrapper supper sipper zapper pepper rapper nipper tapper para knapper topper mapper whapper quipper whipray lipper chipper prao shipper prau yapper
cop coypou scop koppie koppa cuppy cuppa coypu cowpie coop cowpea coupe coup copy cope copay scope