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.
sapphires spires spireas sappers suppress spiraeas spores sapors sprues speirs spares spiers sprees suppers sapours sippers soapers zappers spurreys spurries saporous spurs spars supers spears speers spoors sopors spruce sparse cypres cypress zippers sparrows spurious