Sometimes it's nice to get to explore how your character feels after something's happened in role-play. Other times, it's nice to explore your character's past in a little more detail from his perspective. Whatever the case, diaries and journals are fun, first person posts that may be done as often as you please. For an added twist, if your character is one to have people over or room with someone, why not state at the end whether or not the diary or journal is left out where it's easily found.