I always have my 30D with me, or, if that's not an option, my ixus 960is... I have a few camera bags - i'm a bit of a bag hoarder...
I have just picked up a Lowepro CompuTrekker AW as my main camera bag, it was between the lowepro and another crumpler... [I have a few] The crumpler lost, you can read the review here ->
http://digital-photography-school.co...ckpack-review/