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.
separate sprat sprite spared suppurate sparred speared seaport sport spirt spurt sprit superette sprout spirit sparid sporty sparoid speered speired spiered supered support superadd spread
separate parade pirate prate apparat biopirate cooperate operate reoperate repartee suppurate departee depurate uprate
spar spare sparrow sparry spear