Welcome to Fodors maryb. I like the Lowepro "Slingshot" series, see link below.

I have used my Slingshot in both Vietnam and Cambodia without any problem or worries. If I wander into an area where I might consider myself at risk from being pickpocket then I just swing the bag to the front. Also, the bag has pretty good rain and dust protection, something you should consider when choosing.

http://www.lowepro.com/slingshot

I really like my pacsafe bag which I got after reading a recommendation on fodors. have one this size which is ideal

http://www.amazon.co.uk/Pacsafe-VentureSafe-Secure-Travel-Black/dp/B003DW3CVQ/ref=sr_1_6?s=sports&ie=UTF8&qid=1362555895&sr=1-6

Big enough for netbook, phone camera and guidebook/magazines etc plus you can put water bottles or a fold up umbrella in outer side pockets so not opening it up all the time. However small and tidy enough to take into restaurants etc without feeling you have your rucksack with you. Before I got it I had been concerned that all the mesh security features might make it heavy but this is not a problem at all. They also do a security wallet that I attach to a clip inside and I am ready for anywhere. I just wear it over my shoulder and felt entirely secure everywhere we went in Vietnam and Cambodia but the strap is long enough to wear across your body if you were somewhere where you wanted to be double sure.

loncall,

I also have that bag but I use it for non camera equipments as it has no internal padding, compartment for lens, flash etc. IMO not suitable for DSLR and expensive lens.

Hanuman, I agree pacsafe not a specialist camera bag with tailor made compartments albeit that our camera often travels in it !

I have a DLSR with lenses and I don't use a specialist camera bag. I just throw everything in my un-padded eagle creek bag and it does fine. You will have the camera out of the bag more than in. I recently replaced my old bag with the Pacsafe 300 backpack, although I haven't used it yet. I like the idea of a back pack for my next trip since I will be moving a lot and need to take my valuables with me. I recently purchases some neoprene sleeves for my camera and second lens. They seem to work if you are worried, but I have a feeling they will be swimming around in my bag with everything else! My best advice is to get something that is comfortable to carry.

http://www.amazon.com/gp/product/B006QLPEUI/ref=oh_details_o04_s00_i00?ie=UTF8&psc=1

This is the slingsafe I am referring to. It's a day pack with small dimensions.

I agree that the Pacsafe is fine for everyday camera but my camera cost over $2,000 and each lens cost over $2,500 so NO WAY are they going in the Pacsafe!

A brand new camera bag in a developing country like Vietnam just screams " rich tourist with lots of valuables inside, please steal me"! I use an old daypack with individual hard covers for camera, lenses and iPad. Slightly less convenient as you have to open the bag and then the case to access the equipment but much less of a temptation for bag snatchers than a camera bag. Plus, most people take great care of their equipment so the risk of theft is probably higher than dropping the bag.

The Slingsafe is very very comfortable and a nice size. (I didn't get it because I wanted a single-strap sling style pack, but if I was getting a 2-strap backpack, this definitely would have been it).