Neem is widely considered to be one of the most useful of all cultivated trees. The uses are diverse and extensive. Neem is very drought tolerant and is grow extensively in arid and semi arid regions of tropical Africa.
Roots grow deep and wide, the tree does not stand waterlogging, leaves will ceas to grow, turn yellow, and eventually the roots will rot.
The wood is of very high quality, red in color, similar to that of Mahogany. Also notable is that it is resistant to rot, due to its fungicidal properties. The wood is also used to produce a carbon of superior quality. The tree grows rapidly and regenerates easily after heavy pruning.
Neem is widely acclaimed for its insecticidal and fungicidal properties and has been used as such for thousands of years. Neem oil is, perhaps, the most effective natural product to combat such plagues. The oil is also used in the fabrication of soaps, lubrication oils, toothpaste and other cosmetic applications. Pure neem oil is said to be 98% effective as a spermicide when applied topically. The tree is also an excellent pioneer reclamation species to plant in exhausted soils. It is extremely drought tolerant.
Despite the fact that Neem is toxic to fungus and insects, it can be used as a highly nutritious and productive livestock forage crop.
In East Africa Neem is used as firewood, charcoal, timber, furniture, poles, utensils (pestals and mortars), medicine (leaves, bark, roots, fruit), fodder (goats eat leaves and oil-seed cake), bee forage, shade, ornamental, soil improvement, windbreak, veterinary medicine, oil (seed), a powerful antifeedant (azadirachtin from seed and leaves), soap manufacture.
For in-depth information I would suggest starting with The Neem Foundation, which can be found on the internet. Here's a link to the Kenya Neem Foundation.