Each year, it seems my camera bag gets a little heavier, despite the fact that I continue to refine my packing routine and carry only what I need. The problem, of course, is digital. That means extra batteries (my camera battery looks and feels like a brick), battery chargers (even bigger, but not quite so heavy), laptops, portable hard drives, DVDs, card readers, PDA/phone. You get the picture.
As for camera equipment, I do try to keep it as simple as possible. A heavy-duty, pro-body SLR camera and lighter-weight backup body in case of emergency. A 24-105mm zoom (my workhorse for landscape architecture, gardens and broad landscapes), a 70-300mm zoom for plant portraits, gardener portraits and more detailed landscape views, and a 100mm macro (ideal for plant details, abstacts and extreme close-up work). There is a WhiteBal card to assist with color correction, along with polarizing filters, split neutral-density filters, a blower for dust (my #1 enemy, especially in arid, windy and sandy places), flash cards and the extra digital accessories noted above.
My most important accessory is a tripod--a light-weight, compact, carbon-fiber tripod that fits in my suitcase when flying. It's essential for my garden and landscape work because I'm out there in low light, shooting at low ISO, and most often want front-to-back tack sharpness in terms of depth of field. Long exposures, except on windy days, are a given for me.
Odd things in my bag: a shower cap to protect my camera in case of a sudden rainstorm, small notebooks for jotting down plant names, addresses, or quotes during interviews, and an expired drivers license, phone card and 20 bucks (in case, heaven forbid, I lose my wallet again).
Other things I wouldn't be without on the road: my iPOD (the key to surviving long flights and airport delays), my journal and a good book.
This week, I'm traveling with my rolling bag. It's easier on the back when traipsing through airports and works out fine when I'm shooting pools or landscape architecture. When I'm out in a garden, hiking short distances or photographing natural landscapes, I much prefer a backpack or fanny pack--depending on how far I'm going and how much gear I really need. The less gear I have to carry, the better.