The inside of the bag holds a ton. It has a laptop pocket as well as a couple of smaller pockets, which I use for things like extra pens, chapstick, hair ties, a nail file, and a few other little necessities. I also keep a spare cell phone charger in there at all times, just in case. In the front pockets I toss my car keys, some business cards, and my cell phone.
I keep my packing for a day trip pretty simple. That top pouch holds my headphones (Skullcandy Aviators in white), and that Mac power adapter, which I need in case the room I'm presenting in doesn't have Mac-ready projectors. My laptop slides into the special pocket, and I always have a notepad & pen, which is what I end up using most often on the road. Sunglasses are a must for a trip to California, these Fendi shades are from Nordstrom Rack.