In reply to yarbles:
Lowe Pro Orion is pretty damn good
depends on what lenses you take I guess. In mine I usually carry the following:
SLR with integrated grip
24-70/2.8
70-300/5.6
50/1.4
SB-910
Misc cards/batteries/filters
paclite smock
fleece top
and attached to it a 3 series gitzo.
Failing that I have a slightly bigger more sturdy bag (pro trekker maybe?) but it rarely gets used to be honest.