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.
hippest hippiest heppest happiest hoppiest
hippest heppest pest goopiest pipiest pappiest quippiest lippiest loopiest loppiest sappiest soapiest nappiest soupiest zippiest dippiest tippiest typiest whippiest chippiest ropiest gappiest cuppiest roupiest hoppiest peppiest nippiest hippiest happiest pesty pesto seepiest ripest mopiest soppiest zappiest deepest dopiest typeset weepiest cheapest choppiest pst