I'm looking for a good messenger bag. Does anyone have any suggestions?

I'm sick of wearing a backpack.

Either normal size or half size. I think I would rather the fabric/canvas type, but I'd be open to any suggestions. Enough space for a book, various manbag-type stuff, and a notebook (paper notebook not Apple Notebook. I thought I would make that distinction).

Bonus points for any messenger bag that can be turned into a backpack. I think I have seen those before.

Ideas?

edit: I just want to say I will not be riding a bike with any of these bags. I teach seniors at a high school and I am very young looking so I figured I would lose the backpack to set myself a little apart from the students.

Ok, if anyone would like to know what I personally have narrowed down to, I think, here are my choices...
I think in order of what I like.

*Chrome - Citizen Black Carbon Fiber or Kevlar

*Keen Commuter Bag

*Ben Sherman Canvas Commuter Bag

*Fossil Manchester Messenger

*Ben Sherman Commuter Bag