I found out this tidbit tonight while watching The Crocodile Hunter on Animal Planet. I always thought (although I have no idea why) that many lizard species were venomous, but good ol' Steve Irwin set me straight. The only two lizards who actually have venom in their saliva are the Gila Monster and the Beaded Lizard. Both live in the Southwestern USA and Mexico.
Very few fatalities have occurred from bites of the Gila or the Beaded lizard. One reason for this is that neither of these lizards are seen above ground very often. They have very low metabolisms, can eat HUGE meals and store large amounts of fat in their tails. Because of this, they can eat an entire years' worth of food in three or four large meals, and spend the rest of the year basking in shallow nests. Neither lizard is particularly aggressive and even if a bite does occur, not much venom may reach the victim. You see, lizards don't have hollow teeth that inject the venom like some snakes do. The venom glands of lizards are located at the sides of the lower jaw and open along the outer gum. The teeth are grooved to help the venom flow into the wound, and the teeth are built for biting and chewing rather than puncturing. When biting, the lizard will hold on tenaciously and chew, and venom is injected into the wound. Yeouch!!!!