I am looking at the Rush 24 pack by 5.11 Tactical. It is a military pack but I think it fits my needs perfectly. I have a nice little pack by Field & Stream I got at Dick's Sporting Goods, but it doesn't hold everything I want to carry. Plus it won't hold a fleece or extra clothing. The Rush 24 pack is pretty lightweight and compact. It expands to fit the load so it shouldn't feel any bigger than the load you are carrying.
It also has add-on accessory pouches for water bottles, first aid kit, etc. I want a bigger pack because this year I started carrying some first-aid and emergency supplies. I don't even have a tarp for shelter yet and my pack is full.