Like many photographers, ive fallen for the bag-trap. You never have enough, you always see another model that is bigger, better, more versatile etc...
At the moment i have 6 bags. Not an overwhelming amount, but still..
Here is the list;
A Tamrac Expedition 8
A very comfortable big rucksack. Has been with me on many journey's, where i need to bring a lot of gear. Airline compatible, fits in overhead luggage bins. Only thing missing is a dedicated raincover, but ive never had any water leak through despite that.
A Tamrac Pro 8 shoulderbag
Nice compact shoulderbag. Not really my thing though. I usually carry a tele-lens and 1 or 2 other lenses. That just doesnt fit snugly into this bag with a gripped camera. If you are a one lens or a 2 short lenses kinda person... Get one.
A Lowepro Vertex 100 AW
As far as im concerned; The best bag i have. Nice and compact, comfortable to carry, and with enough room to bring along a ton of stuff. Comes with a dedicated raincover, as with most Lowepro bags.
A Lowepro Slingshot 100
Neat little bag for a 1/2 shortlens setup.
A Lowepro Pro Trekker 600 AW
When i bought the 300mm F/2.8 i thought i might need a new bag to hump it around in. Well... Lets just say that the 300 fits nicely. With room to spare for every other lens i have. It is a great backpack. Comes with a detachable fanny-pack, a hydration pocket and a neo-prene sleeve for a laptop. Its almost awesome.
One of the shoulderstraps tore within the first week. Still functional though, but...
On and off i also use a Maxpedition Jumbo S-type slingbag. Mostly when i travel light ie; only a compactcamera and an I-pad with camera connection kit.
This is also my everyday carry man-purse.. (I know) Its very rugged, and if you put some dividers in there its a great camera bag.