Some bulbs produce babies, but you can also multiply them yourself if you have the nerve. Apparently you can cut them into halves or quarters (or smaller sections if they're big), put them in sand, and little bulbs will form on the bits. Lilies can be increased by separating them into individual scales and waiting for the little bulbs to form. Not for the faint-hearted!
Amarylis is an other easy one to propogate from a bulb. It forms little bulblets which you pull off carefull and replant.(in a little pot) takes a while to flower but I just keep giving them away. My original came from a 90 plus old nieghbor (mrs mallard) about 20 yrs ago. I figure its my way of spreading her memory around.