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.
costs cosets coasts cossets casts coesites castes cuestas casitas caestus caseates cassatas casettes gasts gusts kists cassettes custos guests quests gussets gustoes keysets gaseities
boosts costs mosts roosts ghosts hosts posts justs joists hists guests cosets gestes keysets geests bassets caestus easts basts vestas beasts coasts hastes rosets bastes fists pasts assets pistes vests gists nests lasts pastas foists oasts cestas shists wists wests wastes toasts testis tastes dusts zests xysts cysts cists wrests bests mists russets masts sits possets kists castes pastes lists jousts musts feists hygeists ousts besots hests besets pests casts pastis boasts busts resets reests gests soots phaseouts heists gusts posits vasts quests resits maists fiestas gussets missouts hostas lusts cossets jests gasts visits fasts rousts fests vistas stoss hygieists sots leasts missets sets cuestas knessets rests roasts hoists rusts feasts wrists cestus cistus siestas xystus deists tassets testes tests waists wasts whists chests yeasts
costa cost costae cast caste coast coesite coset cosied cosset