Though I have my own style of carrying my cam, I think this camera bag system is the way to go. Check out the link to a pro photographer's review of the bag.

http://www.karlgrobl.com/EquipmentReviews/ThinkTankBeltSystem.htm

I just bought myself a Kata 3N1-20 bag. This can be a backpack and a sling bag. And just lately there's an add on accessory to be able to carry a tripod along with it.

I also use a backpack and usually I use it as a front pack.

another interesting topic on how to carry gears...

http://www.kenrockwell.com/tech/two-pocket-shuffle.htm