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.
grapes crapes gropes gripes grippes grappas grips craps gorps groupies crappies groups cripes crepes croupes carapace croppies creepies crops carps corps carpus corpse corpus creeps croups kreeps croupous
rapes serapes trapes grapes crapes sarapes drapes tropes pyropes preppies liriopes gropes gripes ropes traps rupees creepies crappies rappees ripes croppies crepes carps hyperopes sharpies cripes warps croupes fraps tripes herpes harps harpies raps priapus frappes tarps groupies troupes rewraps grippes craps towropes reaps drupes wraps bewraps sharps
grapey grape grappa grapy crap crape crappie crappy gorp grip gripe gripey grippe grippy gripy grope