For years I used the Lowepro SlingShot 100 as my camera bag. My requirements were:
1. Wear it over my shoulder
2. Be able to access the camera without taking it off
 
The SlingShot held my camera and 3 lenses, and served me very well. However, now that Garry and I are running Posterous, we have a laptop with us 24/7. So I needed a new camera bag that also holds a laptop. Surprisingly, not many companies make this.
 
With Garry's recommendation, I bought the Crumpler Dreadful Embarrassment. It's designed to be a great laptop messenger bag. It has a built in laptop sleeve for a 15" MBP, lots of pockets for various accessories, it's high quality, and costs only $60! I also like the simple, clean design. No weird logos, straps, stripes, or other standout features. I can carry this to a nice restaurant and it looks fine.

But what about the camera? You can't have a camera and lenses just floating around the main body of a bag. Crumpler makes a camera insert for this bag, but it's a piece of crap. It's big and bulky, and costs more than the bag itself. After doing a lot of research, I discovered the Tenba photo insert.

It's a perfect match. It fits inside the Crumpler *like a glove* and holds a camera with 3 lenses. It costs only $20 and does a great job organizing and protecting your camera gear.

   
Click here to download:
Crumpler_Dreadful_Embarrassmen.zip (2729 KB)

I can get to everything in the bag in seconds. While it's still on my shoulder, I can open the main flap which is secured simply with velcro. I can remove my camera and start shooting. When I'm done, put it right back in the same way. It's actually easier than my SlingShot.

   
Click here to download:
0Crumpler_Dreadful_Embarrassmen.zip (2487 KB)

This is definitely a "kitchen sink" messenger bag. It will hold anything you can throw at it. When I go out in the day and want to carry it all, this bag nails it. When I go out at night, I leave behind the extra lenses, carrying just my laptop, 5DM2 + 35mm f1.4. It even fits under the seat in an airplane.
 
If you're looking for something smaller, check out Garry's review of the Chrome Mini Metro. But if you need a bag that will hold and protect *everything*, I think the Crumpler Dreadful Embarrassment and Tenba Photo insert is an unbeatable combination.