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.
seepy seep sepoy spy spay sepia soppy soupy sappy soapy sip spa sop sap cep sup zep cepe sipe soap soup spae spew spue supe
seepy weepy cheep weep tepoy deep sepoy seep repay peppy peep neep keep jeep heapy veep beep wheep sheep