Decent summary by Andrew McGregor, published by the Jamestown Foundation 1 Aug 06:

Hezbollah's Tactics and Capabilities in Southern Lebanon
With its attack on Hezbollah in southern Lebanon, Israel is fighting on terrain that has been prepared by the Shiite movement for six years since the Israeli withdrawal from Lebanon in 2000. Israeli Defense Force (IDF) soldiers have described finding a network of concrete bunkers with modern communications equipment as deep as 40 meters along the border. The terrain is already well-suited for ambushes and hidden troop movements, consisting of mountains and woods in the east and scrub-covered hills to the west, all intersected by deep wadis (dry river beds). Broken rocks and numerous caves provide ample cover. Motorized infantry and armor can only cross the region with difficulty. Use of the few winding and unpaved roads invites mines and ambushes by Hezbollah's adaptable force of several thousand guerrillas...