Ramps (Allium Tricoccum) are a type of wild leek which smell slightly of garlic. Unlike our domesticated leeks they also have edible, broad green leaves.
Ramps are found in North America as far south as the Carolinas, and as far north as Canada. Their season is short, and runs from March to May. They are availble now at Berkeley Bowl for $9.50 a pound. You'll find them piled in a plastic bag along the eastern wall of the produce section. One word of caution, the roots will be muddy.
I first saw ramps on Iron Chef America, where Mario Batali was using them in a dish. The website for his restaurant Babbo, featured ramps as an ingredient of the month. They also offer up this recipe.