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.
cassis cassias casas cases casus quassias gasses causes cussos cusses cosies quasses caseose causeys gussies casease cuisses caseous gausses coses gases coseys kisses kussos gaseous guesses koussos
lassis tussis cassis chassis missis sis fusses basses noesis cuisses newsies lasses tusses gussies assais bassos lysis bosses cussos kisses messes hussies quasses loesses meiosis missies miosis mousses fesses kneesies niseis diesis chesses massas daisies wussies wisses sassies whoosis cissies passes dosses busses pisses asses posies sissies hissies tassies busies pusses wrasses biasses poussies gausses missus cassias bossies masses fosses mosses jesses sasses fossas cosies oasis koussos gasses cusses seis quassias hisses lassies easies kussos josses nesses phasis musses physis byssus gneisses esses isseis gnosis losses poesies lassos psis misses cesses pussies lyssas sisses tosses posses susses dassies guesses disses tasses passus basis whosis wusses chasses chausses yesses
cassia casa case cause causey caws cays coss cuss cusso gassy ocas