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.
spears spars speirs spiers supers speers sparse spares soapers sappers suppers sippers spireas spurs spiraeas sparrows sapors sopors sprees spires sprues spoors sprays spores zippers zappers sapours saporous spurious spurries suppress spurreys sapphires superrace spruce sprucy sporozoa
pears appears reappears spears coappears operas rappers leapers rippers peppers soapers copperas rapiers hypers cuppers pares capers apers perse speers parrs spiers vipers peres copers mappers wrappers lopers ropers loppers beepers suppers yaupers shoppers shapers chippers wipers whoopers whappers uppers topers tappers dupers dippers zippers piers hoppers spireas peris peepers sparse peers papers pipers boppers hopers pars speirs cappers loopers nappers kippers coppers lepers sippers keepers gawpers spares spars heapers paupers coopers copiers mopers jeepers nippers hoopers gyppers sappers poppers reapers knappers moppers gippers paras parse lappers rapers supers spiraeas repairs zappers quippers dopers gapers paris lippers japers pairs toppers weepers whippers diapers whoppers cheepers tapers choppers shippers tippers yappers yawpers
spear spar spare sparrow sparry speer speir spier spray spree super asper peasouper