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