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.
whooper whopper whapper whipper whippier wiper weeper weepier whipray
hooper cooper whooper looper bopper coper coopery hopper hoper popery mopery mopper roper ropier copper chopper copier goopier doper dopier lopper moper mopier opera popper ropery soaper loper topper loopier toper whopper shopper per
whoop whoopee whoopie whop swoop swoopy wop