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.
diapir diaper dippier tapir dapper dipper dopier tippier taper doper duper deeper dupery tapper tipper typier topiary
diapir tapir gappier pier leaper heaper hippier happier roupier soaper sappier soppier speir rapier aper vapor spire pappier zappier nippier diaper loopier dippier mopier taper tippier weepier cheaper choppier pipier repair quippier spiry cuppier copier gaper ropier seepier sapor soapier raper soupier reaper japer spier paper peppier nappier zippier lippier hoppier loppier dopier goopier caper pair typier whippier chippier shaper