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.
spaced spiced spoused supposed sappiest seepiest soapiest soppiest soupiest
paced peaced spaced hypoacid pieced appeased coppiced spiced
space spacey spacy spaes spas spays spaz spazz specie spice spicey spicy