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.
knack knock neck nick nock nag
knack knock shacko whacky whack wacko wack tack wrack rack pack nock nick neck mack back lack quacky quack jacky jack hack sack tacky wacke wacky whacko shack yack