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.
sprees spares sprues speers spires spores spireas spurs spars spiraeas suppress spurreys spurries sopors spoors spears sapphires sprays sapors spiers speirs spruce supers cypres sparse suppers cypress sappers sippers sapours soapers saporous sparrows spurious superrace cyprus sprucy sporozoa
prees purees rapparees sprees suppress guipures pores preys cooperies repress moperies perries poperies naperies peers duperies prese pyres koupreys fopperies cypres sapphires speers spires presa spurreys press aperies spares pareus sprues spireas apiaries pareos pares roperies peeries japeries depress spores spurries apres cypress pries paries parries peeress peres oppress topiaries
spree spar asper super spurrey spry spare sparrow sparry spear speer speir spier spiraea spire spirea spiry spore spray sprue spur spurry supra osprey