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.
tough toughy toughie teugh tofu toph tophe tophi toff tufa tuff
cough tough lough rough sough ugh pugh waugh teugh sugh saughy laugh vugh ouph roughy faugh toughy saugh kiaugh yogh
dough doughy boughed bought dought doughty tout