I am not concerned with aerodynamics and speed so I always ride with my CamelBak (100 oz reservoir) and I don't fill it completely so there is room in that pocket on top of the reservoir to stash snacks, etc.

There's room in the front pocket to carry my wallet, cell phone, housekeys, lip balm, sunscreen, small tube of extra Hoo Ha Ride Glide - love that chamois cream! If I get warm I can tuck my jacket into the bungee-type cords on the outside along with my bike pump.

I particularly like the CamelBak because I'm pretty sure I wouldn't be coordinated enough to pull a waterbottle out of a cage while riding. With the CamelBak I don't have to stop to drink so I think I keep myself much better hydrated.

I keep my tubes, CO2, etc in a small under-seat bag.

Have fun on your ride!