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.
sprig spriggy sprag sprug superego spark sparky
prig sprig prog capric cupric sprag sprug
spar spiry aspire spurry spur spry sprue spree spray spore spirea spare spire spiraea spier speir sparry sparrow spurrey supra osprey