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.
harper
carper dorper chirper sharper warper harper creeper grippier syrupier roupier crupper rapper rapier raper crappier grouper cropper gripier reappear preppier puerpera draper dripper droopier torpor tripper trooper chirpier reaper grapier riper wrapper drippier ropier roper grapery griper frippery crapper dropper trapper ropery creepier trippier gripper groper larruper proper sirupier croupier ripper trouper drapery crepier