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.
trouper trooper trapper dropper tripper droopier trippier dorper draper torpor drapery dripper drippier
grouper trouper dropper droopier dorper syrupier sirupier proper groper larruper crupper croupier cropper roupier ropier ropery trooper roper
troupe trop troop trope strop stroppy