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.
soapy soap sappy soppy soupy spy sop sap spay soup zappy seepy sepoy hyssop sip spa sup zap seep sipe spae spew spue supe
soapy heapy teapoy dopey soupy loopy sappy ropy hoppy copay copy gappy gapy goopy happy loppy mopey mopy nappy pappy poppy ropey roupy soap soppy zappy dopy choppy