Hi,
There was a thread about this awhile back by someone who had been bitten by a monitor....most people said their saliva is not toxic, but I tell you something: 6 people have reported very nasty effects from being bitten by Varanus griseus (N. African species) and I can give several sources for that. Furthermore, a Zoo Atlanta zookeeper was grazed by a V. griseus and ended up having surgery!
Althought V. komodoensis has some very lethal bacteria and alike (see Joel M. Montgomery's paper: Aerobic salivary bacteria in wild and captive komodo dragons, Journal of Wildlife Diseases 38:545-551, 2002) other Varanus may have their nasty inhabited saliva as well; FYI: V. salvator, V. melinus, V. jobiensis, V. juxtindicus, V. indicus, V. salvadorii, V. doreanus, V. niloticus, V. bengalensis.
Right now the subject is open for much debate and experimentation and so on to solve this question - a question that seems to arise more frequently than not; perhaps because people are keeping more varanids? People are getting bitten more often? their saliva is toxic? Their victims are toxic? Who knows...
Good Luck,
mbayless