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