To dream of seeing or using a sponge implies that you are open-minded and willing to accept different ideas and viewpoints. The dream may also be a play on the phrase 'sponging someone off.' Perhaps you need to become more self-reliant and prevent others from dictating your life.
To dream of leeches feeding on your blood signifies a part of your waking life that is sapping your energy and enthusiasm. Leeches in your dream may represent persons around you, old habits, or ill feelings. This will affect your mental and emotional state. On the other hand, if your body is covered in leeches, it indicates repulsion for what you have done or guilt towards someone you have wronged.