Bulb type plants form an onion shaped energy pack either above ground or under. Some in the hobby grow them for their flowers, while others grow them to display the bulbs. Some of the most popular that are grown by succulent plant enthuiests are Ornithogalum, Skilia, Ledeburia, and Drimia.
Most bulbs in cultivation today originate from the cape portion of southern Africa. The region has many micro-climates in which different bulb families have become specialized. There are more than 1100 species of bulbs from this region. Many are described in the book "The Color Encyclopedia of Cape Bulbs" by John Manning, Peter Goldblatt, and Dee Snijman. Although the book emphsises bulb flowers, it is still useful as a cultivation guide.
Another great resource we've is a web site created by the Pacific Bulb Society. The site not only has extensive species descriptions but indepth growing tips.