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.
spirit sprit spirt sprite spiroid spurt sport sprat sprout spired sporty sparid speired spiered support seaport separate suppurate superette spread spared spored sparoid speared speered spoored sporoid spurred supered sparred superadd
spirit parity periti purity pyrite yperite cuprite spirt sprit sprite typewrite
spiraea spiry spire spirea sprue aspire spree spurry spray spur spry sparrow spore sparry spare spar spurrey spier supra speir osprey