Poems, whether they rhyme or not, are a good release. I used to write a lot of poems and general prose (read as: Rants).

Another thing to consider if you're worried about people finding your journal, is keep a private one online, i have one on LiveJournal which i keep private and have no friends. I haven't used it for a little while now, but it really helped me work through things after me and my ex boyfriend split.