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