Sometimes you can make a big difference by 'zapping' the cache files from your system. You can do this from the terminal, but also a simple process by downloading a utility that provides you with a GUI to do that. Example, Onyx, or Maintain1 (either can be downloaded from versiontracker) I prefer OnyX, which allows a single password to get at all functions. removing all user, library, and system cache files will likely improve what's happening, but a slow shutdown, as Bigpixel says, may be due to a process that is stubborn to shutdown. Try the caches first, come back if you don't get much improvement (all processes can be viewed in Terminal, by typing top (press enter) I disagree with bigpixel on this. If you've not seen top before, it's just a big list, but it shows you processes that are consuming processor time, check it out.