I bought a
Tamrac Cyberpack 6 several years ago when I was in the US and absolutely love it.
Happily fits 2 Nikon DSLR bodies + grips (or 2 pro bodies), 50mm f/1.8D, 300mm f/4 AF-S, Nikon 28-80 f/3.5-5.6D, Sigma 10-20mm f/4-5.6, an SB-900 flash in its pouch underneath the 300/4, an SB-600, MC-20 remote + MC-21 extension cable, a few Lumiquest accessories and some spare 77mm filters in the main body.
It has a separate compartment in the front with several memory card pouches (with little red flaps that you can pull out over the tops to denote full cards), elasticated pouches for spare batteries, charger, cables, and many transparent zippable pockets for more filters, reversing rings, cleaning cloths, snoots & grids for the speedlights and clippable straps to attach a tripod.
It also has four connectors on the sides to add some of Tamrac's M.A.S. accessories (to add side pockets, lens pouches, flash pouches, water bottle holders, etc), and a couple more connectors on the straps for their S.A.S. accessories (more memory card holders, cellphone pouch, etc).
Oh yes, and it has a laptop (up to 15") pouch in the back.
They do a bigger "Cyberpack 8" version (holds up to 17" laptops), but to be honest, once it's all loaded up with camera gear, laptop, chargers & AC adapters, even the Cyberpack 6 gets REALLY heavy, especially if you add a couple of large lens pouches on the side, so I don't think I'm going to be upgrading any time in the near future.
Without MAS/SAS accessories added, it fits perfectly in the size limitations for carry-on luggage.