If you need something big, go for the 5.11 72. If not so big, try their 24. Maxpedition also makes a lot of great bags for carrying anything and everything. These are all comfortable to carry/wear, and have endless options for attaching anything you want (molle system).

I travel all over the world, and I use the 5.11 72 as a carry on bag. In the main compartment I have two laptops in padded zipper packs and a break-down table, and still have room for a change of clothes and a few other items. That's just the main compartment. There's also a pocket for a water bladder, which I use for business papers that need to remain flat. Several other pockets as well. I've carried two bottles of scotch from the duty free in the two side pockets.

If you don't need to carry so much, look at the 24. These are military grade packs, so they're not reflective, but you can put anything you want on them. They have dozens of molle attachments.

I also like Oakley backpacks, but they look too much like something someone would wear while riding a motorcycle.

 

I use a big Camelbak. Super high quality, teathers, expandable, hydration and I use it for hiking, camping, going to the range to shoot, ect. Crazy versatile. Use it for everything and it looks cool too. You get what you pay for. I have a small one and a huge one.

 

I second the camelback. They're very nice, and I see a lot of them in Iraq, same with the others I mentioned prior.

I figure if a backpack can survive the crap they dish out in these hellhole combat zones, it'll be just fine for someone who wants to wear one while riding a bike.

If you prefer a more crotch-rocket look, check out the Oakley Kitchen Sink. It's a bad *** bag.