Ok, there's probably a bit of overlap with the other bag-fi threads here, but I figured it's interesting enough to start on.
Someone at some other forum that I can't remember (DPReview, probably) once said that you can never have too many camera bags. I sort of agree -- different bags are used for different situations, and sometimes it's difficult to decide on the right one to use for a given situation. Throw in a laptop and heavy glass into the mix and things get even more complicated.
Over the years, I've accumulated, traded, bought and sold a considerable number of bags from various brands -- Lowepro, Kata, Tamrac are the three main ones I stick to.
My current favourite is the Lowepro Fastpack 350. It's quite a good all-rounder; it carries a laptop, has all the advantages of a backpack (i.e. weight distribution) and a sling bag (i.e. quick access to gear when you need it). However, one thing that it is sorely lacking is an all-weather cover.
When I pack up for an event, however, my current go-to bag is the Lowepro Classified 250AW. It's a shoulder/messenger-style bag that holds a laptop and enough room for some serious gear. Fully loaded, it's too heavy for casual, all-day use... for events, however, it's very easy to access gear and most of the heavy stuff will be out of the bag, either hanging around my neck or setup nearby so weight isn't an issue.
When I want to travel light, sometimes I use the Tamrac Velocity 9x, Lowepro Classified 160AW or Kata DR-466i backpack depending on my current fancy for the day. The Kata is a no-brainer if I still want my laptop around though.
So... let's hear about your camera bags. :-)