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.
spirt spirit sport spurt sprat sprit spired sprout sporty sprite spiered support spiroid speired seaport separate superette suppurate sparid spared spored spread sparoid speared speered spoored sporoid spurred supered sparred superadd superroad
spirt rapport depart pert port prat apart aport part seaport report spirit sport sprat sprit spurt support deport
spiraea spiry spire spirea sprue aspire spree spurry spray spur spry sparrow spore sparry spare spar spurrey spier supra speir osprey