* o (as in "go", "no", "so")
* oa (as in "boat", "coat", "goat")
* oe (as in "toe", "hoe", "Joe")
* ow (as in "cow", "now", "how")
* o_e (as in "hope", "bone", "home")
Keep in mind that these are just some common spellings, and there are exceptions to these rules. Sometimes, the letter "o" will have a different sound, and sometimes other letters will have the long "o" sound.