I've tried a variety of vegan whipped toppings in the past. I've made my own with tofu and lemon juice and other stuff, and it was OK, but not at all like whipped cream. Most vegan cookbooks with a dessert section have a recipe like this.
Then there's the Lucerne-brand non-dairy dessert topping at Safeway. It's basically hydrogenated oil that somehow resembles whipped cream, but is obviously full of trans fat and leaves you feeling dirty afterwards. It'll do in a pinch, and if you're looking for it, it'll be in the dairy case next to the canned whipped cream. It's the kind that's propelled by nitrous oxide--you know, laughing gas. (In college, I worked in the dining hall, and a friend of mine would take all the used cans of whipped cream and inhale the nitrous. He also snorted a crushed Vivarin once. And MSG. He snorted straight-up MSG. Later he passed out and woke up with a horrible headache. I wouldn't recommend this to y'all.)
OK. Enough college tales.
My point in this entry is that there is now a really good vegan whipped cream: Soyatoo Soy Whip! It looks and tastes like actual whipped cream. Nick bought it for me at Food Fight, a vegan grocery store in Portland. You can buy it from them on their website.