We don't think you should scrimp too much on a bag, given it'll be carrying $3,000 worth of kit. Your host uses a Lowepro Fastpack 250, costing $99.95, its only drawback that it has no space for a tripod or cables, so you have to sacrifice a couple of lens slots just to tote your power lead. Other staffers suggested using a standard bag with individual Crumpler pouches (a suitable Crumpler like the "7 Million Dollar Home" is $150) or the KataKTD, which sadly doesn't pack a laptop sleeve. How about you, commenters? What's the budget bag you wouldn't let your DSLR venture away from? Together, we can work it out.
"I've recently gotten into semi-pro photography and I've come to the problem of how to transport all my gear. I'm looking for a camera / laptop bag that has enough space for a DSLR body (Nikon D90), a 15-inch laptop, 3 or 4 lenses and a speedlight or two. My budget can't stretch beyond $100 and I need it to be durable and weather-proof. I don't have any preferences with style (backpack, messenger bag etc), I just need a large, affordable bag to carry all of my gear. Thanks for the help and keep the gadget passion guys!"