I currently shoot Nikon cameras, I always have at least two with me at events to save time changing lenses and of course for backup reasons.
The majority of my work is shot with two lenses. Nikkor 17-55mm f/2.8 or my absolute favourite lens the Nikkor 70-200mm f/2.8 VRII. The 70-200mm lens is a perfect all round lens, it is great for sports, portraits and even landscapes. When the need arrises I also have some fast prime lenses and of course the monster zoom 500mm lens for surf photography or large circuit motorsport events.
All photographers love their bags and end up with loads - I'm no exception, I've been through many bags over the years and have settled down to my final 2 camera bags which cover all my needs
Shoulder bag - Think Tank Retrospective 30 [link] - this is my go to bag for most things, it's a huge bag and you can fit several lenses, bodies and even speedlites at the same time.
Backpack - Think Tank Streetwalker Hard drive v2 [link] - a monster of a name for a monster of a backpack, this I normally use for weddings or travelling as I can fit all of my camera equipment and also my laptop. You can easily shoot a wedding out of this bag without any issues at all!
I know I said two bags, but a quick mention of a third, my daily laptop bag, it's actually pitched as a camera bag, but I don't feel it has enough room for my dSLR and lenses but if you shoot smaller bodies it's a great bag, and for my daily laptop needs it's great - it's the Everyday messenger from Peak Design [link]
Peak design capture [link] - I have two of these, one on my hiking rucksack and one on my Retrospective 30. They are basically a really quick and convenient way of attaching your camera to the outside of your bag safely and securely to free up your hands for whatever you want. It's really quick and easy and your camera is effectively always at hand. I'm probably not doing it justice so head over to their site and watch some of the videos.