For some reason or another when I shut down my ibook(the latest one) it takes like 15 minutes to shutdown and when I want to restart it doesn't. Also some programs I open freeze and I can' force quit, this is my first mac and usually I would like defrag on my pc, but now I have no clue what to do, let me know!
I would install Onyx and run the cleaning and maintain options. Then I would install Anacron. Then I would look in my Applications folder for Font Book, as mguertin suggests, and see what you can do to clean out duplicate fonts.