I use my stick blender a lot. It saves me the effort of transferring soup to a regular blender, or of pushing it through a mouli-legumes; and, because it is less efficient than those other devices, it leaves behind a rougher, more interesting texture.
I also use the stick blender when I make a tomato sauce with onions - I like to incorporate them in the sauce.
1 onion, chopped
1 clove garlic, chopped
2tbsp olive oil
400g tin tomatoes (I use Cirio)
In a heavy pan, and over a gentle heat, sweat the onions and garlic in the oil with a few grindings of salt (as recommended by Lisa in her comment on this entry) until golden - 10 to 15 minutes. Add more oil if the vegetables threaten to catch. Tip in the tomatoes. Add a little water to the tin, swirl it around to dissolve the tomato adhering to the sides, and pour this mixture into the pan too. Bring the contents to a simmer, and break up the tomatoes with a wooden spoon. Now get to work with the blender - it will work less efficiently if you allow the sauce to reduce and thicken. (If I sweated carrot and celery with the onion and garlic, I am not sure that my blender would be able to break them down.)
Return the pan to the heat, add the sugar (tinned tomatoes usually benefit from a little sweetening) and bay leaf, and simmer until thickened. Check the seasoning.
We ate this sauce with meatballs. (A recipe for which, with a slightly different version of the sauce, is here.)