While canola oil may have the lowest amount of saturated fat, and olive oil more monounsaturated fats, grapeseed oil is still a useful addition to a healthy kitchen. Pressed from the tiny seeds of grapes, grapeseed oil is a good choice for salad dressings - it has a neutral taste, though some brands may have a slight grape flavor or aroma. It is also ideal for use as a cooking oil, especially for high-temperature cooking such as sautéing or stir-frying, since it can be heated to higher temperatures than canola oil before it starts to smoke. Try it out and see if you like it - look for an organic brand, store in a cool, dark place and don't buy more than you can use up in a month or so.
Feel free to substitute grapeseed oil for olive oil in any of the salad/dressing recipes in my Healthy Kitchen.