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.
casas casease cassias cases casus cassis causes causeys caseous caseose quassias gases coses coseys cosies cusses cussos gasses cuisses gaseous gausses quasses
casas masas feases fossas phases vases bases casus essays lases bioassays lyssas massas missays oases paisas peases resaws ceases teases wiseass leases basis eases visas sass sassy baases assays assais says gases saws phasis cases biases mesas naysays oasis pases rases resays seesaws tussahs chases
casa case cassia cause causey caws cays cacaos cacas ocas