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.
droopier dropper trooper drippier dorper draper drapery dripper trouper trippier trapper tripper torpor
ropier droopier trouper trippier rapier preppier grouper groper grippier gripier grapier cropper croupier crepier sirupier crappier roupier ropery roper proper syrupier drippier creepier dorper dropper trooper chirpier