Here is my bike set up for work:
I love these bags, I got the set up cheap at Wal*Mart.
It works well because having a back pack just makes me more sweaty, which is fun enough in this wonderful heat we have been having.
They have tons of little pockets to for drinks, etc.
There is actually a bag that hooks to the top of these two and lays on the top, but that is just excessive for me right now and I don't need that space so it sits at home. But these two bags work nice, I put my lunch in one and my work cloths and kindle in the other, use one of the smaller pockets for my keys, wallet, etc.
They are easy to unhook and take into the house with me at the end of the day too.