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.
sparer spearer sparrier sprier spirier spurrer spurrier superior
parer spearer sparer dapperer spurrer spirier parrier poorer pourer prier purer vaporer vapourer pepperer repairer sparrier caperer sprier kipperer spurrier paperer taperer
spar spare sparrow sparry sprue supra spree spurrey spur spry spirea spray spiry spire spiraea spear spurry spore osprey