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.
spider spidery spader speeder spitter spudder speedier spottier scepter spatter spotter spouter sputter sputtery sceptre septaria
rapider spider tapadero spudder padder peatier pettier pitier pottier poutier powder powdery puttier spader speeder speedier spidery spottier tapadera chapiter
sapid sopite spade spado spait sped spied spit spite spode spud espied