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.
dropper dripper drippier droopier dorper draper drapery trapper tripper trooper trouper trippier torpor
cropper dropper trooper tripper crapper preppier reappear ripper roper ropery ropier rapper wrapper dorper frippery crupper gripper grippier groper grouper proper dripper droopier crappier drippier trapper trippier trouper