The one from sports connection is great(the brand is Urban)! Cheap ($34) and strong enough. This is an exact copy of the Crumpler Formal Lodge. Quality's a bit lower than the crumpler (hey, it's 1/6 the price), but it holds up just fine.
I used to own a farmers double, but sold it off after getting this bag (found the farmers double too big - makes you look like a ninja turtle)
The notebook is slotted in at the back of the back pack (it opens from the back) and the camera compartment sits at the bottom of the bag (can be accessed from the front), this is good as you can access your cam without putting the bag down. Security is not an issue, when the tabs are pulled to one end, it is pretty difficult (if not impossible) for someone to open the bag. Short of slitting it open, again difficult as the material is tough and there is an additional removable insert that holds the camera, it is pretty secure. Another plus is that the zip pulls have hoops that you can put a small padlock through (something not possible with the crumpler zip pulls) if you want to be doubly sure.
Used it for a week - on the move everyday - in China. Works perfect.
Comes in 3 colours (Red, blue and white/sliver).