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