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.
superadd superroad supered spread speered speired speared spiered sprat suppurate superette spired spored sparid spared spoored sporoid sparred spurred spiroid support sparoid separate zippered spirt sport sprit spurt spirit sporty sprite
super spear speer speir spier supper supra asper