I have a Tenba backpack with raincover. I always take with me:
Sony Alpha 77
Sony Alpha 700
SAL 70-400mm
SAL 16-105mm
Tamron 90mm
2 extra batteries
Several SD Sandisk Extreme 16 GB
Several CF Sandisk Ultra II
Stormjacket (rainsleeve for camera and lens)
Lenscloth
Businesscards
Pack of tissues
Painkillers
Nikon D800
Nikon 17-35mm F/2.8
Sigma 50mm F/1.4
Sigma 85mm F/1.4
Nikon 80-200mm F/2.8D ED (2-ring)
Sigma 180mm F/3.5 EX DG HSM APO IF Macro (love spelling out that one )
Nikon 300mm F/4.0 AF-S
I'm REALLY thinking about switching out the 80-200 + 300/4 for the 120-300mm F/2.8 OS from Sigma. It's an incredible lens, even with a TC, and weighs just a bit over what both of them would together. Still in the manageable range (6.2lb), especially with a monopod (which I'll also be adding).
Nikon D800
Nikon 17-35mm F/2.8
Sigma 50mm F/1.4
Sigma 85mm F/1.4
Nikon 80-200mm F/2.8D ED (2-ring)
Sigma 180mm F/3.5 EX DG HSM APO IF Macro (love spelling out that one )
Nikon 300mm F/4.0 AF-S
Surely you don't carry all of the above when visiting a zoo?!
I have a Canon 7D body with an EF 70-300L on it almost all the time, with an EF-S 15-85 in the bag when I occasionally need something a bit wider. Other than that, spare CF cards and a cleaning cloth.
Canon 40d
Canon 70-300mm IS
Quantaray 18-200mm
battery grip
Canon SX20 IS
Usually I use my Lowepro Slingshot 200 bag, but when I'm traveling I usually put in a regular backpack so I can have snacks and such since I'm usually at a 'visiting' zoo longer than I am my local one. I've tried quite a few different camera bags throughout the years and have decided I like the Slingshot the most. I like being able to access everything I need without having to take it off.