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.
sapphist sappiest soapiest soppiest zappiest seepiest soupiest zippiest supposed spiced
sapphist happiest mopiest nappiest nippiest papist peppiest piste sappiest rapist soapiest soupiest zippiest dopiest weepiest typiest chippiest loppiest quippiest ropiest pipiest gappiest cuppiest hoppiest hippiest pappiest roupiest lippiest loopiest seepiest soppiest zappiest dippiest typist tippiest whippiest goopiest choppiest pst