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.
science since seance scenes cense sense scenas scions sensei siennas sins cions cines sinus sensa sinhs sains sines zincy sanies seines sennas sinews sneeze sneezy sonsie senecio sinuous sonnies
science faience wincey whence tenace dienes since seance pence mince menace quince hygienes hence fiance fence niece wince yince
scena scene scion sienna oscine sen sin