MoonRat has a great post of funny ways to not-write on her blog, Editorial Ass. Go check it out. My favorite one is:
His thoughts tumbled around in his head, making and breaking alliances like underpants in a dryer without any Cling Free.(Actually, some of these have been around awhile on the internet. You can find more great similes here.) My other favorite:
McBride fell 12 stories, hitting the pavement like a Hefty bag filled with vegetable soup.