Vegetable mills have been around for a long time, and are fairly simple: a revolving plate forces the vegetables (or fruits) through a grill plate (the size of holes varies).
Of course it takes a bit of effort and elbow grease, but unlike a blender - which pulverises everything - a vegetable mill acts as a sort of filter. It can produce very smooth high-quality soups and purées as it excludes everything that won't pass through the grill (seeds, pips, leaves, etc.).
If you intend to buy:
Choose a robust model in stainless steel that won't rust after washing (avoid the plastic ones).